You're talking about the "what ifs". Fact is, you don't have a monthly car payment.
You want to have a car payment AND spend money modding it? How does that make any sense? You said yourself that you are tight on money.
'09 LCI 335i E90 in Oyster over BSM, 6 spd, Sport, Navigation, Individual Audiophile, Executive, Active Steering, JB4, BMS DCI, Euro Tails/Fog Light Switch, various painted and other OEM + mods, 19" M5 reps summer, 18" M6 GC reps winter.