I came from a 2007 Subaru WRX with the following mods :
-Process West TMIC
-Cobb SF intake
-TurboXS catless downpipe
-Tein S-Tech springs with STi top hats + STi struts
-Cobb F/R sway bar
-Protune by Jon @ HBSpeed 305whp/310wtq at 24psi tapered to 20psi, conservative tune .
After i sold my WRX and bought a 2012 135i with every package except premium and HK system, i will never go back to Subaru. I love manual transmission cars, the connected feeling you get when shifting and pushing in the clutch, but i opted for the 7spd M-DCT.
The M-DCT is very reliable, but once you reach around 400ish hp, the clutch begins to slip. But if your going to be running an intercooler. downpipe, intake, jb4, you will be fine when it comes to reliability. The Jb4 is reliable and makes way more power then an STI or EVO can with just a tune, let alone bolt-ons. If i were you, I'd wait until Cobb releases there AP for the N55, which will probably be in the beginning of 2013. The jb4 is not a chip, it's a piggy back system that removes the stock ecu and jb4 re-tunes ignition timing, boost levels, throttle control etc, so its plenty reliable.
All 135i's come stock with Xenon, so you don't need to worry about having Xenon's on a 135i. The 2011+ 135i's also come with M-sport package, as the 2008-2010's don't. Also, the 2011+ 135i's come with N55 (twinscroll single turbo, made by Borg Warner, or at least the same style turbo as Borg Warner). Hope this helps...