if you want a sparc pizza box, i suggest you head over to ebay and try your luck there. you can technically run solaris 8 on a sparcstation 5 (not sure you wanna).
if you have the money, i suggest you get a sunblade 100. they run ~1000 or so.
are you using this to learn solaris? sun distributes an x86 version as well, although there are some differences and the hardware it supports is REAL OLD stuff. i know that you need to have an ATI card and an SB16 (i believe) for video and sound to work, else it'll be ugly. there is a company on the net that wrote drivers for other manufacturers, but of course you'll need to pay for that.
write back if you need more information.
edit: you want to run a webserver... sorry, didn't catch that when i first read it. get youself a cheap sparc5, 10, or 20 to learn. the only problem that i can forsee is that you will need a monitor (they are proprietary) to first set it up. after that, you can use xterm on your PC to administer it. i know the sunblades will work using the standard 15 pin monitor cables from PCs.