i have a borla side-exit on my car right now (with mac lt's and or h). i like the way it sounds but i want sfc's so im looking for a rear exit. i found a guy willing to trade a magnaflow system with magnapacks and bassani tips for mine, but ive never heard a glasspack style muffler and im kind of wary of doing that. do they flow as well (i def dont want to lose any power), are they really loud at all rpm's (as opposed to traditional muffs), and most importantly, is this a good deal? thanks.