I've never heard that Magnaflow was bad, I had that system on my 1st gen Charger. It is expensive so you don't hear about many people having it. Borla and Corsa are in the same league, top price, top quality.
Flowmaster is a reasonable price, but they only use a cheaper stainless steel than the top price ones like Borla, Corsa, etc. With the way the Flowmaster mufflers work, don't expect a performance gain, just sound.
Something to consider is the Dynomax. Full 2.5" mandrel bent, aluminized(not stainless), turbo mufflers for mid $300 range. Another guy thought his was a bit loud and changed the turbos for Dynomax VT mufflers, still totally around $500.