Before you check how much it would cost, make sure you have it packed like you're going to send it (pkg size and weight are instrumental if you're wanting an exact cost). Any changes you make later will change your total. Use original mfg packing (or better) if possible.
It's hard to come up w/ a rough estimate since you don't know where you're sending it. I would think $40 max for the tower itself. Anything else is going to cost extra.
I work for UPS and may be biased, but I personally wouldn't jump on the FedEx Ground bandwagon yet. It's not *really* FedEx yet. FedEx owns Roadway(the dudes that are FedEx Ground, BUT, they aren't integrated yet w/ what ev'one knows as FedEx. The other day I was talking to my FedEx guy (yeah, I use UPS, FedEx, USPS- depends on the situation) and he was saying the same thing. He isn't impressed w/ them, either, actually. They're not accountable to anyone yet (independent contractors, apparently) and are making the regular FedEx guys look bad. That's just the scoop from a FedEx'er.
Your call, though. If you do choose UPS, I would suggest taking it to an official UPS Customer Counter, though. That way they'll check your packing and if it does get damaged, you should get paid because it's their job to make sure that it's packed well enough.
Snakesnfrogs might not like UPS, but they've been around longer and are doing more volume than USPS & FedEx combined everyday. All three companies are doing similar jobs. Just depends on your preference. There are going to be ppl w/ good & bad stories for each company. Choose the one that fits your needs best.