Crossover upgrade-what benefit?

I have a pair of Proson Reality 66 (4 Ohm, two way floorstander from Sweden) that have a simple crossover: one 3.3mf 100v capacitor and one 2.2 ohm resistor. What benefit would I get from changing these to a higher grade. I am looking for cost effective parts.
I don't know any "cost effective" upgrades. The recommended upgrades which I am familiar with are hovland caps(10x costlier) and mills resisters. Replacing the inductors would also make a difference, but you did'nt mention those.
You did not mention what brands are currently in the speakers now. The type of sound, equipment, and music that you prefer is critical in making recommendations. One thing I can recommend to you... Immediately replace your resistor with a 10 watt wire wound resistor from Ohmite(or equivalent). You will notice that grunge, grain, grit, spit, splashiness, shrillness, and irritability will be much improved. As for the capacitor, this is a relatively low voltage unit(though not for OEM) you described. Who makes it? And is it electrolytic(would seem so from the voltage rating)? The related components, desired sound, and musical tastes will play a big factor in what I recommend to you there. I can say that for this capacitor(since it is a low value), you should be using at least a Wonder Cap. Which is very likely better than what you currently have. Depending on how you answer my above question, I might recommend something much better(film and foil).
I just replaced all my crossx parts,Trelja your correct
on those ohmite resistors, has far has caps our concerned
you dont have to watch the vdc in your crossx, not that much current running thru. The best caps our crescendos
but these parts our not cheap,your 2.2ohm resistor well
run $3.75 and caps well run$16.00 plus you should always bypass for ultimate midrange which is another $ 12.00
so thats what $63.50 for the pair. You well however have a great deal more music flowwing thru. good luck