After destroying my 5 speed three separate times, I finally did the 6 spd swap on my 06 WRX TR about a year and a half ago. Found a seller on ebay selling all the necessary components for $3800. The purchase included an 04 STi Suretrac (non-DCCD controlled) transmission with all the shifter linkage (no shift knob though), front axles, auto drive shaft from WRX, the R180 rear end with all the housing brackets and bolts, rear axles, rear knuckles with e-brake cable, starter and everything else needed. The only issue I had was the seller sent a worn out clutch disc and flywheel leaving me to scramble and buy one. I had worked out a deal with him to peice together the parts as I had just recently did the Brembo swap a few months prior (so I didn't need any front brake components and only needed the rear rotors). Bought a genuine STi shift knob on ebay for $50... some people wanted hundreds for one which is a bit extreme in my book.
I did all the work myself with a friend but I've been working on cars since I was 16 so I had no doubts in performing the work. It took a few days total and at the time, I didn't realize I had a non-dccd tranny so I returned the manual DCCD controller I had purchased once I figured it out. I'm pretty satisfied with the swap. I knew the drive ratio was increasing to 3.90 but was expecting that extra gear would equal out to around the same as the old 5 spd set up considering the ratio was around 3.60... that's not the case. Car runs around 3000RPM at 65mph in 6th gear and it's a noticable difference. I love my Subie.