Roland KC-300 vs KC-550?

I was wondering if I should buy the 300 or 550, I want to be able to jam in my basement with the guitar, b, keyboards etc. in one amp! I dont play any gigs so i dont need it to be ridiculously loud but the 550 has 4 input ports and the 300 only 2 (3 with mic) and I'm curious if i should just invest teh extra 250 bucks! (the 300 costs $200 on craigslist and the 550 $450) thanks!