wheel question
 

currently running 14" wheels. I was planning to get some sort of 15x7 wheel, but I have an opportunity get some used 2000 miata ls wheels (15x6 at 13.1lbs) almost cheap.

What i need to know is if the 15x7 is significantly better handling and more responsive than 15x6. will be used for autox and street driving.

Yes. 15x8 is even better.
That being said, if you can pick up the 15x6s cheap you can always rock them until you find something better, then unload them...

I say keep the small wheels unless the 15s are cheap as heck. Run the tires you have till their bald. In the meantime save some money till you can opt out for 15x7s or 15x8s.
Then again you can do like some people and run 15x6s with some wide azenis and probably be alright at sub 200 HP levels.

dude if you wanna make power you need a good light tire and nice wid3e sticky rubber end of story. I love my 15*7's and 225's but they are still to small and i am now shopping for a wider rim that is aas light currently 9.5 lbs apeice the only problem in this is just like HP or anything else the lighter and faster you wanna be the more $ it will cost. My oe 14's would run 600$ on high end rubber to keep shod. My 15*7's and 225's where like 1K $ cause of 187$ a rim and 75$ a tire adds up. UL's are a little heavy but not to bad, 15-10's and some 245's-265's will most likely get you past 300whp though. atleast untill you want noss or another 100 hp. This is all in how much power you want Driving NA my car could barely touch the handling limits of 225's the way i drove the car, but the difference from oe to the uprgrade was a good 40-50 mph sometimes more in high speed cornering situations. corners i took at 50 before where no problem at 90-100 30-40 mph corners where 80 mph, and wet performance was as good as the dry performance of my OE's. I hope this helps you decide. GL. BFG gforce sports BTW :p

That's what I did, I rode on the rubber that came with the car until they were tired. Then I spent $850 for some Konig Rewinds with Falken Ziex in 15" flavor and splinedrive lugnuts. Probably not the lightest wheels, significantly heavier than the stock daisy wheels.