Welcome to AudioCircle, and to DIY, Jmitchell3!
Modding the Polks would be informative and cheap, but in the end don't expect miracles by swapping caps and wiring. It will still sound mostly the same, with 10% improvement. But you will learn a lot and gain skills.
If you like doing DIY (and not just doing it to save money, which it doesn't) then you know you will eventually build new speakers, I strongly recommend for your first project using a popular, quality kit that is known to sound good and which has a following who can offer support and help if needed. Speaker design principles are fairly heady, and it takes time to become proficient. A failed project at the beginning could turn you off from a wonderful hobby. Better to invest in a good kit that you know (with some help) will turn out great, then you will learn so much from that that you can take on more difficult kit, or start to tinker with your first kit and learn even more, etc.
Selah Audio and GR Research are both sponsors of AudioCircle and they both offer well designed kits and excellent support. Check out their circles and websites.
Jeff Bagby has designed a good bunch of speakers for DIYers, and they all seem to be very well received. Kits are available on meniscus audio, partsexpress, and elsewhere. Discussion of his designs mostly on techtalk forum, and avsforum.
Troels Gravesen is a Danish DIY speaker designer affiliated with Jansen speaker parts mfg, which offers the kits for Troels' designs. The parts are excellent quality and the designs are very well done, and Troels offers good support by email.
Reading some
speaker design books like Vance Dickason's "Loudspeaker Design Cookbook" and reading the DIY speaker forums like our
Enclosures Circle, Tech Talk,
DIYaudio etc will allow you to learn very fast, and choose what kits would be best for you.
