Recently got a Pioneer vsx-821-k and the Energy Take Classic 5 pk. I am using it with my (very) old Yamaha subwoofer that is rated at 25 watts output and 4 ohms. Yes I know it's crap, but it's only until I can get a new sub. Is it bad to use with this Pioneer amp because it's 4 ohms? Also I'd like to get any recommendations for a new sub @ less than $200 that would blend well with my system. Currently set up in my living room that's probably maybe 15' by 15' or so.