For Pokemon Soul Silver, and all the good GBA games... Anything else i should get with it?

As you're getting Pokemon, I'm assuming you l ike RPGs, which the DS and GBA have fantastic line ups of.  RPGs like The World Ends With You, all 3 Golden Sun, the Mario & Luigi games, Dragon Quest IX and Final Fantasy Tactics Advance and A2 are all very highly recommended by me.  If we include ports and remakes, the Final Fantasy and Dragon Quest ones are very good as well.

Outside of RPGs: all 4 Advance Wars, Zelda PH and ST, the Prof Layton games and Mario Kart DS are all essential perchases.  I haven't played the likes of the Ace Attorney games, Ouenden, GTA: Chinatown Wars or Jump Ultimate Stars, but I haven't heard anything that isn't great about them.

yeah why not, it's a very good time to get a ds lite i think, as it's very cheap compared to 3ds and has huge catalog of games as well, what makes it better is because it can play Game boy advance as well, which has lots of games as well, that are worth it, so go for it!

Cooking Mama.  It's a manly game for manly men.  Yeah, it seemed kinda girly but look at the premise:  You want to eat but you ain't gonna go in that kitchen and make it yourself, are yoU?  Fuck no!  Tell Cooking Mama to get in there and make you a sammich!!  Then jizz on her face.  That's what I do.

Note:  Do not play with the pink DS when you come to my house.

Wait... you're going to get SoulSilver, but not Black/White? Man, you gotta get Black/White, as it's awesome.

Other than that...

If you're a Castlevania fan then you're set up with some amazing games:
1. Circle of the Moon (GBA)
2. Harmony of Dissonance (GBA)
3. Aria of Sorrow (GBA)
4. Dawn of Sorrow (DS)
5. Portrait of Ruin (DS)
6. Order of Ecclesia (DS)

Circle, Aria, Dawn, and Order are my favorites, but they're all fantastic games and I highly recommend them!

This! The GBA/DS Castlevanias are fantastic (for the most part).

Also, Dragon Quest IX was far and away the game I played the most last year and enjoyed all 120 hours of it.

Also, if you enjoy enjoying yourself, get Elite Beat Agents (you can find it for like $8 used) and be prepared to smile your ass off.

Get it! Best system of this generation, period! 

Eh Pokemon Black/White throws me off because i dont know squat about the new generation of pokemon, while Soul Silver is just the first two sets of pokemon, which i <3. 

Anything mario is definitly worth getting, and Im not too fond on RPG's but if their cheap and they look fun, I'l give htem a try.

Go for it. There are some good platformers such NSMB and Kirby.

Well I'm gonna play the devil's advocate.

If I were you I would save for a 3DS. DS games are going to begin disapearing this winter and developers are already drawing down support. The 3DS is fully backwards compatable with the DS and you will be able to play Black/White Silver/Gold on it as well.

Now If your saying that your tight on cash and can't afford to save for a 3DS. My next peice of advice would be to hold off a year. As I said above 3DS will begin to take over and DS will begin to draw down. If sales for 3DS don't improve I'm guessing Nintendo will do more to phase out DS so that people buy 3DS instead. I'd expect a price cut within a year if not sooner. Also software will become extremely cheap over the next few years as DS phades away.

But if you have to have a handheld now I'd say 3DS is your best shot. If you have to have one now and can't afford 3DS then I'd suggest buying a DS:Lite and instead of Gold or Silver I would get Black or White vastly superior games and they also offer a fresh and new experiance!