300W is fine - you can always turn down if necessary! There are combos from Ashdown, Trace Elliot, Line 6, Peavey and Fender that wil all do a fine job and you can often pick them up dirt cheap from the for sale forum here, gumtree or eBay.
It would also help if you told us where you are, whether you're after new or used, what your budget is and what music you play!