So let me ask, if you were to start from scratch rather than go from the list presented upthread, what parts would you choose to build a midrange desktop?
It depends of how much performance you may need: the more the performance, the more the heat, the more the noise, the more the cost. You have to balance by yourself all these aspects. Even size matters: smaller dimensions usually lead to more expenses.
First of all, as you are on the cheaper side of the life, you have to go for AMD, as Intel systems tend to cost substantially more.
For 2D/web/htpc use (so no gaming at all), even a mini-ITX SFF system would perform quite well.
A typical (for SPCR) one would be: an Antec ISK-300 or 310 case, an ASUS M4A88-I De Luxe mobo, an AMD Athlon X2 235e cpu, a Scythe Shuriken heatsink, a single platter Hitachi 5K500.B disk drive, a Scythe SFF80A or SFF80B as case fan. RAM may be the above mentioned Corsair DDR3.
If you don't store films, music or programs on such a system, a midrange Corsair Nova V128 or Kingston SNV-425/S-2 128GB SSD might replace the Hitachi drive, if you can afford it. And, in my opinion, you also need an external disk drive primarily for back up purposes.
You can't do some math on NCIX/price match as they currently don't carry AMD mITX mobos.
Otherwise you may opt for a mid-tower/desktop more standard 2D/web/htpc system: it's bigger, more obtrusive, but you might save a bit on mobo (while having superior features) and case fan, and have to spend more on PSU and, probably, a video card.
As an ATX (or mATX) system has superior cooling power, you may choose a more powerful CPU than a 45W one, to cope with a big heatsink, which may be the good quoted Cooler Master 212 (but you have to swap its fan: the orange Nexus Real Silent Case Fan has the best performance/price ratio, but it isn't PWM and it is sleeve bearing, if you mind. So it's not the most reliable choice for placing it horizontally - it depends on mounting and case -, while if you wanna go for PWM you have to choose Scythe PWM fans, surely among the quietest). But you also may not choose any hotter cpu.
Therefore, using NCIX parts, a typical (for SPCR) one could be: Antec Solo case, Seasonic X-560 psu, MSI 870A-G54 mobo, AMD Athlon X3 445 cpu, Cooler Master 212 as heatsink, two Nexus orange Real Silent Case fans (for CM and Antec), a basic fanless Sapphire Radeon HD 5450 650MHZ 512MB 800MHZ HDMI video card, a WD Scorpio Blue 500GB for quietness (or even a SATA III WD Caviar Black 640GB for performance), while the ram is the usual Corsair as in the miniITX system.
Now you may suspend your drive (highly recommended, especially with some loud drive as the Caviar Black!), or use a second internal one for back-up or archiving. You may opt for a SSD as above, or you may choose a smaller SSD as a boot disk along with a mechanical drive: among those small (30-64GB) ones, you may opt for a cheap one (but still good for the task) such as Kingston SNV-125/S2 or Intel X-25V, or for a speedier one (Corsair Force, OCZ Vertex 2 EX, Crucial C300, or so the like) for more performance.
Over and above web browsing/htpc use, if you also use to work with this PC, the processing power you may need depends on application (some serious office, image processing, audio-video ripping/editing): so they may require faster (or even bigger) mechanical drives, more memory, a more capable vga card, or more cpu power (or everything at once), or eventually some "trusted" mobos (as for audio).
If you game, or fold with it, well, price can only increase from the above "baselines".
When I said you should do some homework, I mean just you have to consider your performance need, and then operate a cross-selection from Reference/Recommended lists (case, psu, hdd) on SPCR, and what is actually available to you, with reference to your budget (carefully balancing costs and quietness/performance, as already said).
About cases, an SPCR-related list on NCIX is:
But maybe IMO you could worthly consider there:
HAF-912Lian Li NZXT Silverstone
For the PSUs, the choice on NCIX is also limited (for comfortable sleeping): the only stable point I see is that if you don't game at all, a "midrange" system will need no more than 120-150W (at large!), so you have to choose any PSU primarily for its noise level up to that value.
Seasonic Antec Nexus Enermax
Liberty ELT500AWT-ECO 80+CoolerMaster
If you want to relax your requirements (as said, sleeping comfortably while downloading at night), I think that the following PSUs may also serve you well:
So the idea of "voiding the warranty" of an Antec NSK3480 (swapping the case and PSU's fan) isn't too much bad: otherwise, you may simply resell that PSU (as it has a 55CAD list value on NCIX), swapping it as a whole (and not only its fan).
Have a good luck!