I know this thread is a little old but since I had the opportunity to try out one of the ProLine Thumb basses I thought I'd put in my two cents.
Sam Ash had one of these stuffed in a corner of their Hollywood store that hadn't been abused too badly or had dead strings. There's a first time for everything, right? The first thing you notice before you even pick it up is that it doesn't exude funky sex appeal like the German made models. The gloss finish and silver hardware just don't have the same appeal as the natural oil finish or black hardware of the German BO or NT; but they need to get the price down somehow.
Upon picking it up I knew I didn't have a German Thumb in my hands because it didn't weigh as much as a sledge hammer. This may be a real selling point for those that complain about the heft of Warwick basses. Also, due to the maple neck, the bass had very good balance, which is very different from the infamously neck-divey German Thumbs.
As to be expected, the maple neck feels different than an ovangkol neck, feeling more like any old fender Jazz or Ibanez neck. Most of my experience has been with 5 string Warwicks, which have an almost angular feel on the heel of your palm. This was a rounded neck that didn't feel too bulky or chunky.
Tone wise I was impressed. Its a Thumb, no mistaking it. The controls, including active/passive bypass are laid out exactly the same and functioned as would have wanted them too. Everything about the construction of the Korean made Thumb points to it being a tad more hollow sounding, with some of the features that give Warwick their bass heavy "sound of wood" not being there. That said, it performs as well as one might expect an inexpensive version of a boutique bass to perform.
Pros: If you want a Thumb sound, which is one of the more unique tones available, this is certainly a great way to get it. Plus, if you aren't a fan of some if the ergo problems common to Thumb basses, the ProLine does a good job of make a light, balanced bass. The bass didn't feel cheap, but you are trying to compare a Scion to a Lexus, so you are going to come up a little short.
A lot of the Warwick specialty hardware can be found here too. It comes with the Adjust-A-Nut 3 system, two piece 3D bridge and MEC pickups.
Cons: Beyond the tone, which is passable, there is nothing sexy about this bass. I'm a big old fan boy of the Warwick mystique, and yet some how these ProLine and Rock Bass instruments manage to be very overlook-able. A German Warwick practically screams at you, daring you to pick it up as it assaults your eyes and ears. The ProLine merely says "Hi" as it stares meekly at it metaphorical shoes.
Tone wise all of the ProLine basses are a little anemic due to their less dense, cheaper, woods. They come close, but I wouldn't say are as close to the "real thing" as say the Skyline series to the US made Lakland basses.
Finally there is a problem with the price. $1400 is OK, but I can pick up half a dozen used BO German made Thumb basses from Ebay right now for that or less. So what's the point? They need to get this down to around $1000 if they want this instrument to be competitively priced.
Bottom Line: If you want a Thumb sound and something that sort of looks like a Thumb, these are pretty nice basses. If you want a nice new Thumb, this is the only way to do it for less than $2500. If you can stomach taking a chance on a used Thumb, get a used German one; its a better bass and might even be cheaper.
If Warwick wants to sell these they are going to need to take a second look at the price. They may also want to slap someone in their marketing dept and or who ever controls their distribution; they aren't available from the websites of GC, Sam Ash, or
Musicians Friend.