Winpower psu's tend to come with budget case and psu bundles. Some of them are not that bad but they are built down to a budget. As for sumvision, i would'nt touch one of their psu's with a bargepole as they are very cheap and very nasty.
The psu is the single most important component in your pc. If it fails it could take everything else out with it. Never, ever skimp on a psu. It is a false economy and you will most likely regret it in the end. With quality psu's costing less (Antec Earthwatts 380w £35.24, Corsair VX450w £46.99) there is no reason to cut corners.