Well, think of it this way, right now you have a couple of BMWs you want to push up to Ferrari performance level. You want to get some practice in, so you're considering getting a Civic. Same basic principles apply, but if you pursue the project with the Civic you'll only end up with a riced up piece of crap that will cost you a lot of money.
Sure, it will go fast in a straight line, but none of the refinements will be there. Resale value will be shit, and in the end since you really only need to practice working on the engine you might as well just buy that and hone your skill.
Long story short, these guns are rather bleh, and the reviews come from people with no access to better stuff. Buy a mechbox to practice, transfer the parts to one of your guns after, and don't look back.