An original Xbox? I don't know how much that would get you nowadays, but if it's just taking up space, then you could probably squeeze a few bucks out of it. Personally, I don't like to trade in systems to Gamestop, because they don't give you anywhere near what it's worth. For example, they have a promotion going right now where you can trade in your DSi XL towards a 3DS and they'll give you $75 for it. It's nearly half the value, but still seems pretty meager for what's still a good system.
I know certain consoles are geared for certain genres and I don't think the Wii's into RPG's that much. But if you're looking for good Wii RPG's, you could do a lot worse than the better-than-average Final Fantasy Crystal Chronicles series.
The important thing to remember is that you don't need to WIN the race in order to get this! So load up SanFran Sausalito from the last group and give the pack a headstart so that they're about 3/4 of a lap ahead of you. Feel free to even go in reverse for a bit, just to be safe. Once the pack's a safe distance from you, let her rip and corner carefully! The pack is your biggest obstacle for this objective, because if they shoot at you, it'll slow you down. Keep going and don't stop until you see the Objective Completed text pop up. From there, finish the race. Even though you lost, you'll still get credited with completing the objective.
Killzone seems to be done by better devs than Modern Combat and it's more of a flagship title. I really doubt they'd add Move support onto an A-list title if it was going to fail, so I'd imagine the controls are a lot more responsive. Goldeneye on the Wii is an example of how good an FPS with motion control can be, so I'm hoping it's more along those lines.