I believe everything you listed (except the V1R) might come RTR or pre-built. V1R will be a kit.

Around $400, you might get away with the 4-TEC, RS4-3/2, but definitely not the V1R.

IMHO, V1R is not at the same level as the rest you listed. V1R would be grouped in the level of Serpent, MTX2, NTC3,etc. As "da king" mentioned, there is "trinity reflex" which is a V1R clone, which comes hopped up with K Factory items and have posted impressive results in some races.

I would look around for parts support for the Serpent. It has always been hard for parts to come by from Serpent. If you can get parts, the impulse is a good car. BTW, Serpent is changing their car line up. Impulse will be re-born as Serpent 500 (I believe) series and predicted to be coming out this month November.

I personally drive a V1R and like it. I have also driven NTC3, MTX2 owned by friends and like those to. These car handles very well, lots of setup options, needs no or few mods to be race worthy, popular cars by racers and therefore can get help at local tracks.

Here are things you might want to find out before purchasing:
1. Do you live close to an LHS
2. Does you LHS support the car you are considering
3. Do you plan on racing. If you do, does your race track allows you to run .15 engine (which are mostly found in RTR). If not, you will need to change to a .12 size engine

Another way is to go to a local race. Talk to racers and find out the cars they run.

Sorry for the long post. Hope it helped.