You never answered the question why tower. If it is because its close I understand but for availability and the best service I have seen.
Try here for parts and stuff. You can get all the spares you need plus if you call they can get you stuff specificly.
they are updating the server right now but should be up in a couple of minutes.
And as far as which to choose. The Jammin CRT is one tough truggy, and as far as the RTR, it only needs two hopups to make it competative if you want to race it. The Z brace and the aluminum chassis braces total of $65.00 and they aren't nessesities but mearly helpfull hopups.
I hope that this has helped.
Oh the Hyper 7 is on its way out and parts will become harder to get.
The Jammin is winning races like crazy and they have tons of support on line if you need help with setups and tips.