As a former MKIV owner. I have to tell you these pocket rockets are fun to drive. Good torque and plenty of potential. However, i consider their transmission very weak (Manual shouldn't be as bad though).
I'm in the exact same situation and got a MINT 2013 128i with 67K miles for $9,000 lol. Great to put miles on while staying in the BMW fam. I do regret not getting a 135i, there's plenty of low mile cars in the classifieds section for $15-17K. Knowing how you mod, i can picture a monster daily, more like a sheep in wolf's clothing. Hell, you can even slap a 128i batch and start messing with people