If I get the P253's(not any pro reviews on them) I still need a separate bass?
If I were you, I would make the stretch to the p363 or p362. The mid range woofer is a real star of the Primus series, as I understand it, but the p253 doesn't have it. Also, the Primus speakers do not do badly on bass. If your budget is real tight, I would go for the Primus without a sub. It has pretty good bass down to the 40s, and sounds very good with or without a sub. In fact, it would be better to run them full range and properly amplified than to run them with a cheap subwoofer. Since it does very will without a sub, the only subs that do make a significant contribution are serious subwoofers, the kind that start around $400 to 500, in my opinion.
