| You definitely want roundwounds. Flatwounds just don't have the zing of a roundwound string.
Pretty much any nickel round will give you a present, bright metallic slap/pop while retaining a good thump. DRs are coated, so they last a long time, but tend to lose a touch of the character a brand-new uncoated nickel string has. I'm a D'Addario guy; I'd recommend their XLs or EXPs in nickelplate (the EXPs are coated, but not like the DRs; they sound far closer to their uncoated cousins)
All-stainless, like Dean Markley Blue Steels, D'Addario Prosteels or DR Hi-Beams can also give you a good sound. Stainless has a bit less of the low mids, which if you're fighting a nasal honky sound can be just what you need. Really the strings are just one piece of the puzzle, and the right string depends on the bass, amp, EQ settings, and your personal tastes. | 
