My suggestion is that you find what seems to be the best specification for your money (bearing in mind what you will use the PC for) and then go with that retailer. Evesham, Mesh, Multivision, Holly etc all have good quality machines but occasionally do make a mistake / create a dud machine and then get a bad name on these pages.
But for every dissatisfied customer there must be hundreds who are satisfied - otherwise the company would be out of business. Personally I found that Multivision gave me a good deal and I am pleased to recommend them to any who ask.
Unless you are a real hardcore gamer, then I would advise not going for a top of the range graphics card - it will have dropped considerably in price by the time that a game appears that needs that spec.