Building a server- RAID concerns

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I'm building a server that will serve a web-based educational course, and the database that underlies it. The site will need to support ~250 concurrent users, and each user will be hitting the database quite frequently. I've done some research, and it seems that just about any decent CPU will handle the load (I'm getting 2 quad-core Xeons), so no questions there. I'm getting 8GB of RAM for it, which should also suffice. Where I'm concerned, however, is the disk system. I'm thinking that keeping the database and web site on different drives is a given, so I'm looking at at least 2 drives. I also need redundancy for each drive, though, so I'm looking at some mixture of RAIDs. 0+1 is ideal, but takes 4 drives, so I'd need 8. 5 is slower, but only requires a total of 6 drives. I could also do 0+1 for the db and 1 for the system/site drive, which would also be 6 drives. Etc.
Any suggestions on how to split up the drives, and which RAID configs to employ? Maybe I should build two servers (a DB and a web) instead of one? I've got about $5K budgeted for whatever solution I come up with.

I suggest RAID 5. Easiest to implement and the parity and striping practically gaurentee your data won't be completely lost. 0 +1 is a pain in the butt, yet admittedly a better system though. And you only need 2 HDDs for 0+1. But they would need to be some big friggin drives.

Just a quick comment... why do you want to physically split web site and database? Seems pretty irrelevant to me.

I figured that since the server was likely to be making a lot of disparate reads to both the database and the web site folder (and system folder/cache/etc), giving the DB its own drive would ensure better access speeds, since the read heads won't be busy loading other things. The impact is probably pretty small, as there won't be a huge amount of disk activity beyond the DB, so it may well be irrelevant.

I also given some thought to putting the DB on a flash based hard drive, but they're pretty expensive.

Investing money in lashing of RAM will give better speed than more drives.

Don't forget that write times to flash drives are slower than HDDs. If the database is updated frequently, a flash drive could work out overall slower. Also, flash memory does have a limit for rewrites. It's pretty huge, but an active DB might push it.