Hola
I just bought an RME Hammerfall Multiface PCI for the same purposes as you are looking for.
it gets amazing low latency under ASIO, and with some tuning you can get it to run pretty well with Jack under Linux. see here for Linux configuration details:
<IMPORTANT> This was right, but currently NEW Multiface cards can't be used under Linux anymore.
I bought this card in order to use it under Linux and Windows, unfortunately the current PCI card firmware (v11) is not compatible with the current ALSA driver. So the idea is to downgrade the PCI card firmware to v10, unfortunately it's not possible to downgrade the firmware from v11 to v10 if you have the hardware revision v1.8 (last revision) of the PCI card. I know it works with hardware revision v1.4.
The only solution is to wait for the next version of the ALSA driver or to use the Multiface ... under WinXP.
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Apart this card, there are these ones :
*M-Audio Delta 1010 LT (8in / 8out) (cheap) *M-Audio Delta 410 (2/8) (cheap) *see also Terratec cards (cheap) *Echo Layla 24 (8/8) : the only card that has the same quality as the RME Multiface, but less neutral (Echo cards color the sound a bit, like MOTU or M- Audio ; RME cards don't affect the sound at all)
For modern electronic music the RME looks like being the best choice
Good luck
J