How can I improve this DIY kit

So I built a pair of parker audio 98's about 6 years ago. You can find the kit here

98 & 98 kit

I used a 2uf cap on the tweeter and the stock enclosure specs. Now I would like to improve the design. I have two ideas on how to improve the design but could use input.

My first idea is to improve the crossover. The only real improvement I can really see is to add a low pass to the woofers.

The second idea I have is to add a powered woofer to help fill in the low end. These speakers really don't have much bass and I don't think a different style of enclosure will really change this. I even thought about mounting these in a back loaded horn but unless someone else tells me different I think that a semi active design may be the way to go.

Aside from these change does anyone else have any ideas how I could really maximize the sound from these drivers?
Yikes!!......A system impedence of two Ohms? Ouch! For the 6.5"....
Looking at their site we have: Fs 60 Hz, Qts .26, Vas .78 Cubic foot, Four Ohm, 93 Db@1W1M. Not the best of specs...particularly the 60Hz Fs. That's a long way to reach down toward some deep Bass......& it won't get there.

I have considered a different kit but I figured that I should make the best of this one before I do that. The 2 ohms really isn't a problem with my amp and they can easily be wired in series to become 8 ohms if need be. The way I see this system, now that I have built it and learned quite a but, is trying to get bass from a midrange driver. The thing is that you can't get bass from a midrange driver. What do you guys think about adding a bass driver that is possibly powered? I would have the MTM played by my zen select and add a 12-15" woofer