Wierd, my first reply disappeared from the topic. Deleted?
Anyway, since you're a first timer, I'll make this easy on you...
Since you need this computer for recording purposes, I'm going to tell you everything you need to Pimp This Out (tm) for low/no noise.
First, take a look at this thread: http://forums.silentpcreview.com/viewto ... ght=5801k6
All fans will vibrate when used. The trick is to minimize it to keep down the noise. Buy the McMaster Carr parts 5801k6 and 5801k8. These are fan isolators. They are a bit difficult to get on (MUCH easier to install if you pull the isolator with a pair of pliers while pushing the fan against the case), but eliminate a LOT of the vibrational noise. The k6s are best for 80/92mm fans, the k8s for 120mm fans. Alternatively, you can use earplugs (cut in half), or place rubber washers between the case and the fan. Isolators are the most effective though.
Buy a multi-fan controller. This will allow you to turn down the fans to a point where they are quiet, while allowing you to turn them back up on hot days. NEVER run them at 12 volts unless your system really needs it. 12 volts usually equals noise. Shoot for 5 to 7 volts. Some people use this http://www.silentpcreview.com/modules.p ... =86&page=1
. But you will need fans with a THREE-pin connector to attach them to the controller. Also, the blue lights won't turn on unless the fan supports RPM monitoring (not a big deal... it's an aesthetic thing). It comes with two cables that allow you to have the fan plugged into the fan controller while still preserving RPM monitoring on the motherboard... Useful for a system fan, and 1 (or two) CPU fans.
120mm fans - Panaflos are VERY thick, so you can use one on the back of your Sonata case, but not the front (it will fit, but touches the drive case and transmits vibration). See here http://forums.silentpcreview.com/viewtopic.php?t=6127
I don't think the Pabst 120mm work with fan isolators. Some people recommend JMCs undervolted to 5volts, but I have two and am NOT impressed. Have not been able to aquire any NMBs, so I don't know about them. I'm one of those few who are of the opinion that 80mms are quieter than 120mm.
Go to the main page and check out the recommended section. For recommended parts in general. I will warn you, though, that with the PSUs, some people have had problems with the Silentmaxx 350w PSU (no fan, entirely passive), with it either buzzing more than it's supposed to, or blowing up. For a high end system like yours, I would probably recommend the Seasonic Super Silencer 400w, it's the quietest of the fan based PSUs according the the recommended list.
Acoustic Dampening - Results have been mixed, but the only to have consistenly reported as being remotely effective is the Acoustipak Deluxe v2. (quietpc and siliconacoustics.com carries this). It costs $80, and it will increase your temps. Even with 2 120mm fans, the Sonata has been reported to run fairly hot (hence, the reason they put in the ANTEC air holes... it needed the air). So it may not be recommended, as the foam would increase temps by itself, and again by blocking the needed airholes.
I've heard that the Evercase model on the recommended case list may have better airflow, and has been rated as quieter, but I don't know how it would handle a dual Xeon setup. Pretty cheap from New Egg though.
If this is the picture of your motherboard http://www.newegg.com/app/Showimage.asp ... 114-04.jpg
you should be fine, as it uses passive cooling instead of a fan.
What type of video card are you running? Zalman has a couple of GPU coolers which are fanless, or if you are in the market for a silent one, go to the quiet VGA section of the forums. Some people have just started a running list of silent cards.
Hard drive - look at the recommended list, but I've had great success with the Samsung 120gb 8meg cache PATA. Barracuda IVs are rare nowadays, and don't perform that great (from what I've heard). The Spinpoints are fairly quick. If you choose to you a drive enclosure, go with the Smart Drive 2002. I've seen a LOT of stories from people who wound up frying their drives in the Silent Drive, so go with the Smart Drive instead (which also acts as a heatsink, keeping the drive slightly cooler). An enclosure will cut down on idle whine (almost inaudible from inside the case from the Samsungs) and seek noise.
Alternatively, you can get a No Vibes III (or DIY with bungee cord) to suspend the drive. This will greatly cut down vibration between the drive and the case, at the cost of higher temperatures (due to the lack of heat conduction from the drive from metal-to-metal contact) and poorer performance (drive errors due to "shaking" within the elastic bands.
OR... you can use the grommet mounts for the hard drives that came with the Sonata.
Hopefully, this will get you to the quietness you need.
Oh, and Zalman is coming out with a $1200 dollar case in the next few months that is completely silent (entire case is a heatsink, instead of using fans). It only comes with a 300w power supply, which you won't be able to change out (I think). Unless they offer a 400w for those needing more power, I wouldn't recommend it. Those two Xeons are going to need a lot of power.
As to the CPU HSF... Looking at the pictures of your board, you can easily go with 2 aftermarket HSF... 2 things. 1) Use Arctic Silver Ceramique thermalpaste (not capacitive, top of the line). and 2) keep in mind that if you go with the thermalright 900U, that will be a LOT of weight on the board. I use one, and find it perfectly fine, but I'm not sure if 2 would be a good idea. But the Silentmaxx link you posted is the first HSF I've seen that offers decoupling for the fan... but it's expensive.