I have a two 97 540i/6 with several modifications. I personally think that the non-vanos 540's are excellent cars. I just recently purchased a low mileage 97 540i instead of selling my car and buying an M5. The 540s were meant to be the next M5 when they originally came out. The 97-98 540s weigh 275 pounds less than the M5. Many of the non-vanos M62 engines dyno at much higher numbers than the factory estimates. It is not uncommon for them to throw down 270 at the wheels, and assuming that every 100 pounds = 8hp the 540's HP could be compared to an M5 with a little over 300. Since most dyno around 325 from what I have seen, there is not a huge difference.
The M5 has a lot of nice features to offer.
With the modifications I have completed, my 540 has been able to hang with every M5 I have come across. Including a Dinan S2, which maybe got a fender length to 100. I still love the M5 and will probably own one some day, but for now I am sticking with my 540s.
List of Mods
Dinan CAI
Dinan Stress Bar
SS headers
Custom Magnaflow CATS
SS x-pipe
SS Race Exhaust (m5)
M5 Trunk Pan
M5 Bumpers
BBS RKII 18X10 & 18X8.5
Autothority ECU
Zimmerman Cross Drilled Rotors
Xenon angle eyes
