Hope some of you fellow RAP-er's can lend me your experience.

I'm in the process of planning/finalizing a DIY recording workstation to be
used for recording, mixing, and editing. My plan is to use it with either a
Mackie 1620 firewire-enabled console, or a Presonus Firebox firewire
mixer/preamp. In either case I will be sending a firewire signal of up to
eight channels into the DAW, and monitoring at least a two-channel mix out
back through the firewire to the console/mixer. I've done research and
narrowed my choices, but the final selection could use some actual
real-world input, and since all my recording activities heretofore have been
to tape (analog or DAT), I'm flying a bit blind.

The two workstation finalists are two Shuttle small footprint and
ultra-quiet boxes, each outfitted with a main boot HD (160mb Western Digital
"silent" ultraDMA drive) and a separate recording or media drive (SATA
Western Digital 10,000rpm "Raptor" 74mb drive). Either will also have 1 Gig
of appropriate ram, and plenty of USB 2.0 and Firewire connections. The
difference between the two (aside from about $200 in cost) is that one would
use an AMD 3000+ XP Athlon and and Socket A motherboard using DDR333
(PC2700) memory, while the other would use an AMD 3000+ Athlon 64 and a
socket 939 motherboard with DDR400 (PC3200) memory. In each case the memory
chips would be of good quality and low latency (cas of 3). Both
workstations would be running Windows XP professional SP2.

My main question therefore is -- will there be a real world difference
between these two systems when it comes to laying down tracks, and if so,
how would it manifest itself? I'd particularly appreciate hearing from
folks who've actually had experience with both, or faced this choice
themselves.

A separate question concerns the quality of the mic preamps/mixers. The
Mackie 1620 contains their ballyhooed Onyx low-noise mic preamps. The
Presonus has their usual mic preamps. Each contains eight inputs and will
be used to record chamber music, jazz, and small-group rock and folk-rock.
Some of the recording will be live, some done in good semi-studio
surroundings. The Mackie setup will cost approximately twice that of the
Presonus, but it's extra control features would only be of use (if at all)
for the rock recording, which will be less than half of what I do. I put a
premium on really good sound quality (especially for the chamber and jazz
work) and would love to be able to afford a bank of Great Rivers,
Milleniums, or Grace's, but I simply can't afford them right now. I will be
using a mixture of Sony condensers, dynamics, and a Royer amplified stereo
ribbon mike.

So the question is: for this use and with these mics, will there be a
dramatic difference between the two choices in quality of preamplification
and resultant sound. Or should I make the choice based on convenience,
size, and cost factors? Or is there some comparably priced firewire
input/output/mixer/preamp combination that I should consider in additon.

Any and all help in answering these questions will be appreciated. Thanks.