I like your list but would like to point out a minor error you've made, the AE is actually all metric, the Losi on the other hand is imperial and will require a new tool kit... They are great cars though.
All the ones you've listed there are brilliant. The Agama is doing well, go on Nemo's website and check it out
http://www.nemoracing.com/Nemo_Racing/Welcome.html
An older Xray would be just as good if you're just starting out, you could pick one up 2nd hand for a fraction of the new cost.
I like the JQ's THE car too, saw one at Slough at the weekend, was also running THE engine. Went real well, spoke to the guys running it, not a bad word to say. That said there were loads of Agama's there and all did real well.
As I said previously though, at a beginners level you won't notice the difference between the cars, they're all very good, it's when you get up to the top the difference and fine details show up more.