As other people have mentioned, Aaron's R34R possibly IS one of the best in the country so unless you've seen it in action, I'd be careful of what you say about the car.
As for GTA, I bought my car from GTA back in 02. If you would like an honest opinion of them, PM me as I can't tell you everything about them on this public forum. I can tell you that they weren't very helpful when the car failed and I needed a repairer ASAP due to their negligence.
When I had the car checked out, they simply said that they'd pay for anyone I chose to do the check as long as I bought the car. At the time though, I didn't know of Racepace but if I had the knowledge I have now, Racepace is definitely the place to go to check out your future car.