I have swifts on my car with no issues... koni yellows would be an improvement on the track but make the ride a little harsher on the street.
Swift springs review!!!!!
I would stay away from megan coils on this car. Ksport? I guess that'll work??? But if you do some research you will find that the "BUDGET" coils that seem to work best on the 370z are BC Racing BR coilovers, Stance & Tein base coilovers.
If you're going to spend money on coils though? You might as well save up and get KW3's,TEIN monoflex, HKS hipermaxIII or JIC Magic flt2's (iran these on my g37. awesome performance).