Your future computer will be a delicate balance of power and silence, and it will also require some compromises to work properly. First of all, you didn't state your budget, so I will assume no more than $2,500. You CAN use the Shuttle boxes to achieve the computer that's in your mind. If you're an Intel fan, go for the Shuttle SB61G2 and PIV 2.4C or if you like AMD (or want to save some cash), go for the Shuttle SN45G and the Barton 2800+. These chips are powerful and very good values (and they both hover around the $170 mark). There are probably some better deals and better bang-for-buck CPUs, so check the market regularly, but make sure you get the 800MHz FBS PIV “C” and the 333MHz/400MHz FSB 512KB cache AMD Bartons. Also, go for the cheaper OEM processors, since the Shuttle systems include their own customized heatsinks. Regarding heat, the PIV 3.2C actually runs much hotter than even the AthlonXP 3200, so the old AMD heat argument is no longer valid – AMDs Barton and Thoroughbred are much cooler than the old Thunderbirds of yore. Since both of these motherboards use dual-channel chipsets, use two sticks of RAM for the best performance (especially important for the Intel box). I like the Corsair TWINX1024-4000, which is a pack of 2 512MB DDR500 sticks, for a total of 1GB RAM. This is a very good amount of RAM and will not require upgrading for a while. These modules are also overclockable (they have 100MHz headroom), but this doesn’t necessarily mean they will run at low latencies. However, as has been discussed on Anandtech, LostCircuits and AcesHardware, modern chipsets are more memory-bandwidth hungry (especially PIVs) and latencies are hardly important anymore (the difference between 2 and 4 CAS cannot be felt and is barely measurable). Therefore, don’t worry too much if you can’t hit the best latencies. Also, if you don’t plan to overclock at all, just buy the much cheaper XMS3200, which will run at DDR400 (the FSB of both systems). Then get the 2 hard drives. This is entirely up to you: you can the very fast WD Raptors, but you may not need their speed, and they are noisier and generate more heat than their 7200RPM brethren. You can also go for the Seagate Barracuda series which are very quiet but don't provide the best performance (I hear the Samsung drives are also very quiet and are decent performers). For a hybrid of quiet and performance, the Maxtor 8MB or WD 8MB series are great (I prefer the WDs 8MB for storage, Seagates for quiet boxes, and SCSI for the OS and apps). This depends on your budget, your capacity requirements, your personal "quiet factor," and your lust for performance. Also, there is only 1 internal 3.5" bay for the drives, so you will have to sacrifice the floppy bay for one of the hard drives. Another caveat, there is only 1 optical disc bay, so on-the-fly copies are out of the question; this may or may not be a deal-breaker for you regarding the Shuttles. Are you ready to jump aboard the DVD writer bandwagon? I am personally waiting a bit, but if I were in the market I would look hard at the upcoming Plextor 8x and Lite-on 8x models, as well as the current champs, the Sony DRU510A and Pioneer A06. If you just need a good CDRW/DVD combo, the Samsungs are the one to beat, with LG and Plextor making decent ones too. Now for the cards: both boxes have 1 AGP & 1 PCI. I would definitely get a dedicated card for the AGP, as the onboard graphics are weak (the Intel one is terrible) and your system's performance will feel sluggish when 3D tasks are encountered. Here is where you need to make another choice: do you want to go for an AIW card for graphics and TiVo functions, or do you want to get a simple 3D card for AGP & a PCI WinTV card? For a box like that, the Radeon AIW 8500, 9700 and 9800 are great choices, because everything is integrated onto the card. However, if you like to upgrade your graphics card more often, get separates so you won't lose TiVo functions when you upgrade the graphics card to next-year's model (though this may not apply to you, because you said you're not a big gamer). The on-board audio is very decent on these boards and both boxes feature optical output. To address the "silence issue:" both of these boxes are fairly quiet, but the fans grow louder as the internal temps increase, so you may notice an increase in noise as you work on CPU-intensive things, such as divx/mpeg/xvid encoding. There are 2 fans on the AMD box (one 40mm PSU, 1 80mm CPU/system fan) and 3 on the Intel box (same arrangement as AMD + a 40mm on the northbridge. This system will be sexy and powerful, and you friends will be wowed if you color match and use an attractive monitor (the Samsung SM-172T come to mind). Every client of mine has absolutely loved their Shuttle machines, and they are great with the wife factor.
I hope this wasn’t too exhausting, but building “the perfect system” requires much research and planning. Have fun.