im sure the quality of the fd will be fine. unfortunetly i only have and know about infinitude's (which is now known as MFactory). it has worked perfectly for the past year now. i never had any grinds or anything unusual caused by the fd. the gears whine from about 35-50mph but i like that noise anyway.
im sure you wont break the gears with only 170 hp. the final drive and inputshaft are made from stronger materials than your gears anyway. im going to be somewhere around there hopefuly by summer after all my suspension is said and done. i would just worry about getting some really good tires. you are definatly going to want to get good tires, because just stock, it rips my tires loose in first gear pretty good. heres a site where im getting my tires from, they are relativly cheap too;
http://www.edgeracing.com/tires/2055015/ i would get the toyo proxies all the way on the bottom. for 100 tread wear, $120 is a bargain.
but top end, you wont fill any slipage with the tires, i garantee it. and gas mileage is BARELY effected with the final drive. i do 65mph at 3500rpm. i love the final drive setup. your second gear feels like a normal tranny's first, your third feels like a stock tranny's second and so forth.. a lsd unit would be a very good investment while doing the final drive swap. also, if you have the extra money and time. pick up a zc third and a vx third (to use as your fourth).
over all, i would make sure to pick up a lsd unit, like obx. they are cheap and reliable. and utilize that lsd with some sticky tires. your car will feel like it has way more than 170hp thats forsure. i think youll be happy in the long run.
take your time on the build and make sure to check your clearances!