There's 2 kinds of fast...Straight line speed and low lap times. Straight line is limited to budget and gear ratio which is determined by engine rpm,s gearing, tire diameter and body aerodynamics. Fast laptimes include all of the above, smoothness and constant lines.
As I tell every new on-roader, learn your car and it's characteristics in handeling first then you can basically determine your speed needs. Remember, fast engine doesn't mean fast on the track or even just doing speed ovals. Consistant laptimes and lines will slowly but surely reel in the competition. See what your car can do now, as it stands. Get it to handle according to your needs.
I know the HUDY system is expensive, but even the RPM Guage ($12-$15) is a needed item to get the alignment close in measurement.