The only reasonable cost way your going to upgrade the crossovers is to either change out the capacitors yourself, or find a local tech to change them out. Speaker crossovers aren't dangerous from a voltage standpoint so you could change them out safely. If you're handy with a soldering gun (which I assumed having a DIY design speaker)do it yourself.
To keep costs down I would only change out the tweeter caps to start with (maybe the mids as well). Boutique caps cost, how much depends on values. I would expect caps alone would cost anywhere from $100 to maybe 1k, all depends on values, cap chosen and who does it. To do all my Merlin caps with Duelunds will end up costing somewhere around 2.5k, well worth the money in my estimation.
To keep costs down I would only change out the tweeter caps to start with (maybe the mids as well). Boutique caps cost, how much depends on values. I would expect caps alone would cost anywhere from $100 to maybe 1k, all depends on values, cap chosen and who does it. To do all my Merlin caps with Duelunds will end up costing somewhere around 2.5k, well worth the money in my estimation.