Watch out. Stainless Specialties is probably more expensive because they use better material. You know, 316L or 316 instead of 304. So, don't be tricked into buying cheap stainless thinking stainless is stainless. The best would be 410 but who can afford that? Inconel would be even better. If you want the best quality welds, you've got to use backup flux on the inside of the pipes, but who cares about the quality of the weld on the inside. As long as it holds exhaust it's ok by me. You can mig tig or gas it and you don't need to use clamps unless you want the system to be easily removed. If you want it to be smooth, just focus on getting good penetration during the weld and grind the crowns off.