Too right, general film, pulse etc. caps from the big electronic component retailers can often mean big savings. 🙂
I agree, a quality PP filmcap is a good one, those for audio are often overpriced and not better. There are measurements done of a few and the difference in sound is so minimal (like less than 0.1dB) that it's not worth considering to pay those prices. I always use those that are the cheapest availeble in small quanities, but if you need a lot or are often ordering from the big suppliers, take industrial ones from Wima or so and it wil also sound good.
The measurements i was talking about are found here: Capacitor upgrade in crossover - Is it audible? | Audio Science Review (ASR) Forum
Have you ever consider using APO Equalizer program for an global eq on the pc soundcard? It modifies the windows driver so it will have the same effect as an DSP only free and way less hassle. Would save you a lot since you can skip most of the crossover.
