See, now you are into the realm where I had to stop myself and look closely: I can do a six conversion for the same (or close) money, have 240HP (before any mods are done- and we all are well aware of the mods available for the M3, including blowers and turbos, if you're REALLY sick... 360hp anyone??)and have reliable performance for 200K miles...
Now maybe some of you out there thinking along the turbo/blower with internal work maybe understand the six conversion is not such a bad deal afterall... 3K for a D/A blower, probably 2K for cams and head work, a few hundred (or more) for pistons, boring, balancing and blueprinting the four ????$... Once you add it all up, it just wasn't worth it to me, to have 'braging rights' (260 from the 1.9 IS impressive) but what about reliability, and daily driveability??? I can hop in my car now, and drive cross country, with no worries about where to get 100 octane, or overheating issues, or throwing a rod, or dry-running (and siezing) a turbo... BUT, if something DID go wrong, I know all the parts are 'off the shelf' BMW factory parts, so parts are as close as my nearest dealer...
Speed IS just a question of money, but smart spending will yeild better (in my opinion) longevity... I'm not afraid to spend my money, but I always do LOTS or research before I drop a dime...
Personal note: my goal is 320 (no blower) HP with equal or better reliability to the stock motor. This is just how I do things. You are all free to do as you wish.
