You should take the match IF you are vested and can take that money with you when you leave. It's free money!
SEPs are for small business owners and the self-employed. With ROTHs, you can't take a tax break on your return, however you pay NO taxes when you retire and withdraw the money. Most IRAs are the other way around: take a tax break now, pay taxes at retirement.
If you only intend to invest the money for 6-12 months, I'm a little at a loss, since I'm a long-term investor. All I can think of is CDs. They don't throw off a lot of interest, but something is better than nothing.
Looks like you can get 1.10% on a 1-yr CD pretty easily. If you invested $50,000, you'd get $550 when the CD matures in 12 months. CDs, or Certificates of Deposit, are very safe--your deposit is FDIC insured--so you're guaranteed not to lose anything.
http://www.depositaccounts.com/cd/