DTS/ PLII outboard?

Hey Guys,

I'm a noob when it comes to audio hardware. I don't have the serious cash to back up such indulgences, yet, but I'm learning. I just got my first surround system, an RCA RT2280 HTIB. I know it's crap, but you must realize that I had never indulged in surround sound before, so this is a significant step up for me. I use the system primarily for playing games and sometimes watching DVDs, but the damn system's lacking two things: DTS and PLII decoding. Gamecube's all about PLII and DTS is the only 5.1 output the PS2 can do real-time (not just with cinematics)- GTA Vice City comes to mind. The system only comes with DD and plain vanilla Pro Logic, which is fine, I guess for Xbox titles. But the world is made for more than just Xbox. I wanna hear my PS2 and GC games the way they were meant to be heard, well, the titles that support the formats anyway. Are there any cheap outboard decoders that decode DTS or PLII or even both? The system's 500W, 80Ws to the satellites, 100W to the sub (NON-powered ). Is an outboard decoder the way to go, or do I need to get a new reciever? Mind you, I'm looking for the cheapest way to do this. Thanks guys!