I was in the same boat as you OP. I got out of audio when David was still as Resonant Engineering, and "custom" subs didn't just have a different basket and dustcap..
With that said, I love CDT.(look at my sig..I think I have all their Es-0 stuff hahah) I really enjoy their warm and clean sound. I listen to a lot of metal and occassional funk, so strong midbass ( Rob Zombie comes to mind) or some old musical funkiness ( War "spill the wine") really are my test tracks when I listen to new speakers.
I can tell you that 50$ more on a well-balanced frontstage can pay off quite well.
Also, if you are a DIY guy, things like some old Mach5's, or some peerless/vifa/dayton drivers would be a good choice, and pick up a separate xover for them. However the cdt's work so well becauss they wete designed as "packages", so to speak. Their crossovers are tailored to make their speakers sound phenominal(as all companies do with their products).
I think you might enjoy the hd62's, or perhaps some vifa Xt25 tweeters and some SLS drivers from peerless if you have the room.
I can only tell you that before I got into the system I habe now, it all started with listening to some cdt es-06's free air..
This isn't my main hobby,either. I have a 87 grand national that is mid-build, so if I can justify taking money away from a car like that to put towards cdt...that should tell you a lot.