How about. You get a Sony Ericsson W810i. That's slightly cheaper than a K790 and it's still a very capable phone. Then with the excess $100 or so, buy one (1) Wii game and save the rest.
My sister owns the W810 and believe or not, I would have chose that phone over my K790. The only reason I didn't get the W810 was because of it's design and the font of the UI (I know that's lame. Spending $100 more just to get a prettier font). Yeah, the screen was not as good as the K790, but I don't think the price is worth it (but the font sure was lol).
At least that is what I would do in if I were in your situation.