530i M is more reliable than a 540i M, they both have the same fuel economy, 540 being alot faster. To me a 530i seems slow, i think it's too heavy for that M54 motor. I'd get last year 540i (2003).
1990 M5 Euro
You wash your car like it was your firstborn child, you tend to its needs like it was your own body, you protect it like it's your family, then you drive it like you stole it