I can only speak to EB rounds (have never tried their flatwounds), but I like 'em, myself. They run around $22-24 (4-string set) at my local shop and that's about what I'm comfortable paying. I am your basic weekend warrior and only get paid for about half the gigs I play, so I've always had a problem paying $40 or more for a set of strings just cause so-and-so big-name bassist plays them. I string my P-Bass with either Power Slinkys (.110 IIRC) or the standard gauge (.105) and they have always worked fine.
JMO but bottom line, you can do a lot worse, especially for the money.