Its the same as any hobby .. making something your own and the experiences you create with it.
Im exactly the opposite end when it comes to "supporting" mods, I believe they are mostly to enhance after the fact instead of a pre-requisite. Take my SS Chevy for example .. almost 400 horses from the factory - and now I am considering the Borla cat back system. Mostly for the sound aspect to hear that 6.0 Liter motor leave Fords in the dust ( in reality, its been mostly WRX and STI's around here ) .. but its not necessary for the performance - its already there and can only be improved on. In the case of my Tbird, id rather put the money that could be spent on an exhaust, etc .. towards a better engine to have a real starting point.
I get that. I prefer suspension/braking before motor. Having more power is useless if I can't stop or get around something.
The exhaust (unless you get headers) is one of the least expensive mods you can do, and has potential to help a performance build later (heads/cams/intake or a better overall motor) while still sounding better than stock.
But as you said, it's all about personal preference.
97 Thunderbird LX (The GT Bird)
PI Swapped NPI motor with some port work on the heads, PI cams, 80mm MAF, CAI that feeds from fenderwell. Jmod, 3.73:1 TL in Mark VIII carrier, Mark VIII aluminum LCAs, 93 Mark VIII driveshaft, PBR brakes (soon to be Cobras), 18x9 wheels, 255/40/ZR18 Tires, Front and Rear strut/shock bracing, GR-2 shocks, Eibach 1.5" springs, 1989 SC front and rear sway bars.