Its Zalytron not Zolatron. www.zalytron.com. Another good supplier is speaker city www.speakercity.com. Also GR Research.

The first thing you'll find in looking at drivers on these sites is the realization that the RETAIL cost of the raw drivers (and the OEMs don't pay anything like the prices we pay) in most finished speakers rarely exceeds 10% of the price of the speaker. This huge differential is of course due in part to the mark-ups in the trade. But to be fair to the higher-end speaker companies, what you are also paying for is (a) a highly engineered passive crossover network that is far superior to what even a knowledgeable hobbyist can achieve with the available home-level design programs and test equipment; (b) a cabinet that is more accurately cut, probably more aesthetic, but for GOOD speakers also highly designed. To use Linn as an example, most of their cabinets have angled sides. I'm convinced that this technique is a tremendous advantage, but its beyond the capabilities of 99% of even dedicated home woodworkers.

Having home-built several speaker pairs in the past, and having used a couple of kits recently to start building up my home theater system, I offer the following advice:

(1) Aside from truly exotic (i.e. $$$) stuff, the pros seem convinced that Focal / Audiom and Scan Speak currently make the best widely distributed drivers (plus Raven for tweeters, see below). Although driver preferences are highly subjective and DynAudio seems to have a number of devoted followers, my own ears say that the drivers mentioned above are considerably more accurate.
(2) The audio world is awash in decent bass and mid-bass drivers, but tweeters are another story. The ribbon tweeters from Raven and the higher end Focal / Audiom dome tweeters seem currently to be getting the nod from the pros - but at a price. In all but one of my home-built / kit-built systems, I have spent more on the tweeters than on the other drivers.
(3) Although Parts Express does offer generic crossovers that feature high-quality parts, the crossover design is the Achilles heel of both the home-built AND the kit speakers (although much more so for home-built than for kit). Smoothing out the impedance and balancing the SPL for the different drivers is highly specific to the attributes of the driver by model number.
(4) Especially with the widespread availability of decent-quality powered subs, I highly recommend that you stick to two-way systems for home-built or kit-built. (This designation refers to the crossover network and therefore includes the popular MTM designs).