PC-Chips has a few boards that match your requirements:
Available:
M599LMR - super-7, SiS 530 including VGA, C-Media 8738 sound/modem, SiS 900 10/100 LAN.
M741LMRT - same for slot-1/socket-370 twin (using SiS 620)
New:
M757LMR, M758LMR - socket-370, SiS 630 all-in-one chipset including VGA and LAN, C-Media 8738 sound/modem. M758LMR has the better expansion slot layout, with the softmodem raiser not blocking a PCI slot.
M581LMR - same for super-7 (using SiS 540)
These new boards have an A-DIMM slot that either takes SDRAM memory for the integrated VGA to use, or a "Video Companion" board (using an SiS 301 chip) that'll bring you TV, Digital Flat Panel, and Secondary CRT outputs. Neither add-ons are available yet.
http://www.pcchips.com.tw/product.html
(Note: All those boards seem to come in "MR" flavors as well. These do not have the LAN hardware.)
Linux support is particularly good for SiS chips, since they aided in driver development and even developped some of the stuff themselves. Even the integrated DVD decoders have drivers. C-Media 8738 sound and softmodem (!) also have mature Linux drivers, and so do the LAN and IDE devices.
Regards, Peter