Since I obviously have access to tons of stuff, and I actually own and drive a 124, you guys may be interested in what I actually run on my 124. This isn't really a sales pitch, it's just how I really set up my own car.
When I bought it I almost immediately went with the following performance mods.
V1 intake $169 (I am rounding everything up), Euro+Drive Lite $650, H&R springs $233, and front and rear Eibach Anti-Sway bars $300.
That's a total of $1352 and it really transforms the car and brings it to a much higher level of performance.
Of course since then I have done other things. New products that I wanted came out, and we developed new stuff. The car currently has the Euro+Drive ECU tune and a V4 intake, along with fancy wheels, stubby antennae and more.
Greg