Remaps dont tend to make things unreliable. However they have a tendancy to hightlight existing issues that may be unnoticable with oem map. Clutch, maf and others so dont buy a map un prepared for potential costs. As for tuners everyone on here has the best tuner! Its really down to opinion mate. Stick with a reputable name.
My money would only go toward badger 5 or r tech. And i mean only those 2 having been stung before twice!!
lastly stage 1 is a generic map dezigned to work with your oem car
stage 2 is a generic map which is designed to work with other hardware such as fmic, exhaust, downpipe,tip etc although each tuner varies required hardware. A stage 2 map on a oem car wont perform any better than stage 1. Probably worse infact.
all said and done research it for yourself so you can be at ease with your choice. Plenty of info on here. Daz