Well i can tell you from experience of having had 5 mustangs ive modified from the ground-up that the 2011-up 5.0 is the way to go. Each car I purchased new, each car I modified to varying degrees. 88GT, 91LX, 2003 Cobra SVT, 2006 GT (4.6), and now the 2011 5.0. The 91LX ran 14.54 when i took it to the strip the first time, and 8.68 @ 161 12 years later when i sold it. The '03 SVT ran 12.90s stock with a decent hook, then finally took the car into the high 9's with kenny belle, solid axle, (D&D modded 6-spd) , the 06 obviously took a built shortblock, aftermarket o/d trans, and alot of boost to finally hit the mark (barely 9.998), and i invested a small fortune. The '11 has ran 9.88/138mph (712 rwhp) and has done it cheaper than any of the previous ponies ive owned. Basically a great front/rear suspension, a clutch from hell (lol), a whipple 2.9, headers, high flow cats, shell urt. as of now, i have ran stock mufflers, Gt500's, and now the new dynomax vt, which has offered about 11rwhp better than the other two and is pretty quiet, surprisingly. im a big fan of quiet. the american racing headers, even when connected to stock exhaust, picked up the exhaust note, but the 3" exhaust with high flow cats and the new dynomax vt muffs seem to be the best combo of sound, torque, and hp. My friend Doug has a '13 Automatic with the same exhaust system, and automatic with a circle d converter (3200) and 3.73s, aluminum driveshaft, front swaybar removed, c & l cold air, and weld rts and drag radials all around. THATS IT for his mods....with n20 from jms chip corp and a custom tune, on pump gas, he's already gone 10.54 @ 129 mph. You can make the new 5.0 as loud.....or as quiet.....as you want to. There at least 10 muffler/exhaust combos to tailor to you the sound you desire. My car still pulls 23 mpg with 93 octane. The efficiency of these new cars is just insane. I'd check the listings here, and auto trader, and find an '11 to your liking. You can go fast with either auto or 6-spd. Should be able to get in one starting about 21k. 25k being pretty common. Hope i helped a little.