How to pick a vendor [closed]
My answers are not in order or mapped 1-1 with your questions. These are just bits of advice to avoid getting burned on hardware vendors.
For hardware itself, look at possible candidates on Newegg. Not to buy, mind you, but to read the reviews. If you are buying something for a particular feature and no one uses that feature, that's a mark against. If there are no reviews at all, that's a mark against. If the reviews are mostly negative, that's an obvious mark against.
Ask the community. Read through support forums for the various brands/communities and see what they say. Are there a lot of complaints about the hardware you're looking at? Do people generally like the product or have a lot of success stories? Is there a support forum at all?
Try before you buy. Seems obvious, but easy to overlook. Get a trial of whatever it is and test the hell out of it while you can still return it. If it's not good enough, send it back. You've lost some weeks now but saved a lot of both time and money in the long run.
If you're choosing between service providers, ask for references. If they're a good company, they should have satisfied customers. Ask them about their competitors.
Do they have a good support plan? If something breaks on a Saturday night, can you call someone to fix it? Will they guarantee a replacement of defective hardware more than 30 days (or several years) after you bought it?
Do you have a good past experience with the provider? If your company has never had a problem with Company X's products, but Company Y could save you a little money, is it worth it? What if Company Y saved you a lot of money?
There's no easy answer. You have to investigate and perform all the due diligence yourself. Weigh all the factors and get a second opinion.