I've recently acquired an 550D and I'm very happy with how it looks. Now I've caught the bug of messing with fans keeping it silent.

I know silent pc gaming cases tend to be an oxymoron, but this is what I'm thinking with the 550d - I want the computer to be silent (with all panels on) when I'm doing things other than gaming, but when I know I'm going to play I'd take off all of the panels for maximum airflow and cooling.

I plan on keeping the stock corsair fans, then buying 4 140mm XIGMATEK eXTREME SILENT Series XSF-F1452 and placing them in the bottom fan, side panel, and top panels. I'll also put a fan controller on them NZXT Sentry Mesh Fan Controller. I know the Noctua is the go to standard here, but I don't want to spend that much money on a single fan, especially when I'm willing to tolerate some noise during gaming.

My question is - what would be the best airflow set up? And does my current plan for having the case fans on only while i'm gaming make sense?

I've seen these examples on the internet, but I'm unsure as to what will work best. The side panel (not shown in the picture) would be blowing cool air in.
Option 1: The current set up

Option 2:

Option 3:

Having fans off at low loads is referred to as "semipassive" cooling. With the right components you can build a system like that fairly easily.

Yours however seems overly complicated and unnecessarily risky in the first place. I don't think panel-moving's a viable solution in the long term, as you'll just get frustrated with it, especially when you find out how many easier options there are. Also, an excessive number of fans - especially when it means opening up big holes in the case - will increase noise noticeably with little benefit for cooling compared to a well-designed and power efficient setup.

Speaking of, what sort of setup will you be doing in the case? I can't see anything outlined in your signature or in the post. This is the principal question, as that determines what sort of cooling you will even need.

The drafts are missing GPU cooler flow, which would most likely be either out the back or out the back and into the case's bottom section. They all look like workable solutions on the surface, but experience says #1 is the most likely to work. I've tried all sorts of silly setups along the years, but the engineers who designed the classic ATX layout had a pretty good idea about what they were doing.

If I understood your post correctly, I needn't go overkill on the fans then - which I would be happy to do. Perhaps I should just go with buying a bottom intake fan then and perhaps consider upgrading the rear exhaust fan?

My set up would be:

* CPU Heatsink in front of the rear exhaust fan, fan pushing out.
* GTX 570 - which is already noisy as all hell when it's running a game (which at that point a silent gaming computer concept becomes moot) - the hot air is exhausted out the rear of the case.

After reading some of the other threads on here regarding the 550d, I've decided to close off the top and side exhaust, then replace the front intake and bottom intake with GT-AP15s, Push on the Radiator with an NF-F12 PWM, and exhaust with a 140mm NF-P14 FLX.

Plugging the top and side sound like a reasonable thing to do (and should be VERY good for silence), as it's just a single GPU setup. Even though 570s feature a pretty hot GPU from what I understand, it is always up to the cooler to keep things cool and quiet - extreme airflow will not help considerably, unrestricted and direct flow is more than enough.

The bottom intake I think is a good idea, since the 550D's front intake is somewhat obstructed by the sideways drive cages and trays. Incidentally this should enable you to simply adjust a static RPM level for your front intake - it will mostly be relegated to cooling HDDs, unless you want to try to achieve maximum positive pressure (to keep out dust for example).

The Gentle Typhoons are excellent fans, but the 1800 RPM model sounds like severe overkill (unless you're really, really determined to have that positive pressure). If the motor and bearing noise are no worse than lower RPM models, however, and if you can dial it down to quiet levels at idle (600 RPM-ish), then it's probably no worse a choice - just with excess capacity that is probably not worth paying extra for (if that would be the case). Same goes for the exhaust, but Noctua fans seem to have pretty wide adjustment ranges and rather uniform mechanical sound, so that's not too bad.

I have used everything from 800 to 2000 RPM fans in various setups and helped build systems with similar variety. My experience tells me even hot SLI/CrossFire builds didn't need much more than 1200 RPM as long as the airflow was unrestricted.

I would go with option 3 with the exception of plugging the rear back fan or ducting it directly to the CPU heatsink. In my experience, having 2 fans 90 degrees from each other doesn't do much good and can create "dead zones" within the case.

My second choice would be option 2 - very silverstone-esque with the positive pressure setup. You can also flip the PSU so the fan faces upwards (assuming you have a bottom mounted 120mm model), and that would also benefit from the positive pressure you're creating and get lots of airflow for basically free.

A fan roundup with some relevant data just got released: http://www.silentpcreview.com/article1266-page5.html

The relevant findings:
(my emphasis)

So, it seems the hi-RPM models have extra mechanical noise, as can often be the case with more powerful motors and possibly heavy-duty bearings (DBB in the case of the Gentle Typhoons).

Bugger. 3 of the 1850s just arrived yesterday. I'll have to test it and see what I can tolerate..