I have to add another vote for the Hyper 8 for all of the points mentioned above. It is also one tough buggy. The only problem (my fault for not being thorough with the threadlock) I have had with mine is a couple of screws falling out. I have experienced runaways where it ran full throttle into a wood support post and nothing was hurt. New parts are readily available on ebay for low dollars. I just recently bought a used full roller plus extra spares for under $200 that will provide replacement parts for a long time. The 8.5 (the replacement for the 8) is out now and the initial reports are favorable for it as well.
My comments are not meant as criticism of the other buggies. I either own or have owned Kyosho, Mugen, Ofna, and Losi and they are (were) all top-notch. If the Losi 8ight (which I currently own) were as durable as the Hyper 8 (or my skill improves significantly) I actually prefer how it handles and drives but the Hyper 8 is consistent and has been the toughest of the bunch.
Your stated requirement of $350 for an RTR does limit the selection quite a bit. Since you already have the Sportwerks why not just use it until you save a bit more? I have learned from personal experience that success behind the wheel is 80% driver and 20% car. How do you make the 80% driver part most beneficial? The same way you get to Carnegie Hall - practice, practice, practice!