The hyper 8 pro will probly be your best bet. It also includes a good pipe that will make a great match with a nova rossi n21bf or a rbmods 3 port econo. Most kits don't include pipes. Either of those two motors would be a great starting point and if treated properly will last for around 10 gallons. Heres a quick break down of what you will need for a 1/8th scale buggy.
A radio with endpoint adjustments and trim adjustments.
something like this http://www2.towerhobbies.com/cgi-bin...I=LXGAG2**&P=0
Two good non digital servos, digital servos don't last as long in nitro cars.
I'd recomend this for throtle/break http://www2.towerhobbies.com/cgi-bin...?&I=LXHHV5&P=0
this for steering http://www2.towerhobbies.com/cgi-bin...?&I=LXANT4&P=0
Then you will need a starter box, a glow plug igniter, fueld, tires, and spare parts if there is not an on site hobby shop @ the track.
b4 you buy anything visit your local tracks and find out what other people are running. We can tell you about these products all day, but in the end the guys at your local tracks and hobby shops will provide you w/ the most help.
The reason 1/10 scale is becoming less popular is because it is much harder to drive. 4wd doesn't require a smooth throtle finger and people want instant results so they invest in buggies and truggies. Odds are 2 years from now 1/10 scale will be stronger than ever because these drivers have learned to drive and want to try something new.