I agree with Ray. My experience with my first bass (plywood Czech) was that it sounded just terrible until I put some new strings on. Then I moved the soundpost a bit and that improved it a little also. I put some cheapy Red Labels on and even those made an enormous difference over whatever dead ones were on there. After I broke one of those, I upgraded to Helicore Hybrids, which was another quantum leap. I just got one of Bob G.'s Bulgarian carved basses and WOW. It has Helicore Orchestras, so it is easy to compare to my old ply with the Hybrids which are pretty similar. My old ply sounds alright, but there is just so much rich tone in a carved instrument that is in the wood that I don't think you will ever hear in a ply. It would have to be a very poor carved instrument to have inferior tone to a plywood, IMHO, setup and strings being equal of course. The most important thing is to have a carved top. I've heard some hybrid Christophers that were quite impressive in both tone and volume.
I think the Mathias Thoma basses are Romanian in origin. There is a company I found called Hora in Rhegin, Romania that will ship basses to the US to retail customers. The cost savings would be comparable to Bob G.'s Bulgarian basses, but I preferred doing business with Bob because of his long standing reputation here in the USA. Also, the shop in Kazanlak, Bulgaria is smaller and the basses are all hand made. At some point I'll do a full review of my new bass which is the larger (43" string) 5-string model, but suffice it to say for the moment that this is a gorgeous instrument with a very full sound and tonal range. Most of the other lower priced imported basses come with lower quality stock strings, so you can depend on restringing them unless you get them from a shop that does that already.
It would be interesting to hear that bass you tried with better strings and a luthier set-up. There are so many things that can make or break the way a bass sounds. I've found this to be true with all stringed instruments from my old Harmony Classical guitar all the way up to my new carved bass.