OK, I might as well get involved.
Currently I'm running 2 machines, but my emphasis is mostly on real recorded audio, not sampling. The sampler may well prove to be a temporary addition to the main goal, depending on how well I can get it all to work together.
1. Main Audio/Sequencer
Athlon 3500+ in shuttle small form factor case. 1GB RAM, 160GB HDD.
MOTU 324 + MOTU 2408 (24 channel TDIF)
Terratec PHASE 88 FireWire
Win XP Pro
24x TDIF digital audio feeds to a Tascam DM24. I also have various outboard processors; a Lexicon MPX100 and a TL Audio Fatman 1 being notable examples.
I use the MOTU and the Terratec simultaneously with ASIO4ALL, giving 32 channels (24 TDIF and 8 Analogue) in and out to Cubase SX 3 (actually, the Terratec has spdif too, so 34 channels, but I have no use for it at the minute). I mostly use the Terratec's audio IO as track inserts in cubase.
Of the 2 sets of MIDI IO on the Terratec, one pair forms a loop with the DM24 for closed loop MMC (this loop also includes the MPX100 for delay time sync to tempo) so that I can use the transport on the desk and sync automation and MIDI control of motorised faders etc etc.
Of the other MIDI IO, the out channel goes to the Sampler PC, and the other input is free for keyboards, drum pads etc as necessary.
2. Sampler PC
Intel Core2Quad Q8300, 2GB RAM, 500GB HDD.
M Audio Delta 1010LT (8 analogue outs feed into the DM24).
Linux Ubuntu 9.04
LS from CVS of a few days ago
Fantasia pre-build, latest I could find.
VSL 1st Edition (on loan).
I really wanted the audio/sequencer on a quadcore too, but the MOTU 324 card doesn't work in newer motherboards. I have a replacement 424 card coming soon, at which point the old Athlon 3500+ will once again be relegated to email/internet duties and another Q8300 will perform audio/sequencing duties for me.
All of this outputs through a vintage Rogers stereo valve amp into a pair of 15" Tannoy Monitor Golds (in incorrect cabinets for now, but I'm working on that... slowly).