Both of the recommended cases are perfectly adequate in terms of features. Things to consider (besides looks) in choosing a case:
- Size: The Silverstone is a micro-ATX case, while the Thermaltake is full ATX. The Thermaltake is 5 inches taller, 1 inch deeper, 1.4 inches wider, and 2.3 pounds heavier than the Silverstone.
- Quality: Cheap cases are never amazing quality, but some are better than others. I personally have sworn never to buy anything made by Thermaltake ever again after a horrible experience with one of their budget cases (and then discovering that practically everyone who owned that case had the same issue, and the case had been in production for several years without changes). Your mileage may vary.
Of the sub-$50 micro-ATX cases I've been looking at lately, the Silverstone PS08 seems to be the best-made and least likely to explode. I think there are several $50ish ATX cases that beat it, but nothing under $40.
- Builder-friendliness: If you're not an experienced builder, it helps a lot to have a case that makes things easy for you. You're unfortunately not in the price range of the really easy cases, but there's better and worse even in low-end cases. Now, ease of building is *not* one of Silverstone's strong points (to say the least), so the PS08 is probably not your best choice on this point. The Thermaltake should be pretty easy as long as parts don't start snapping off or something.
For cases that balance quality and builder-friendliness on a budget, take a look at this lineup:
http://www.newegg.com/Product/ProductList.aspx?Submit=Property&Subcategory=7&Description=&Type=&N=100007583&IsNodeId=1&IsPowerSearch=1&srchInDesc=&MinPrice=30&MaxPrice=60&Manufactory=1516&Manufactory=14581&Manufactory=72745&Manufactory=1333&Manufactory=1459&Manufactory=2120&PropertyCodeValue=548%3A8478&PropertyCodeValue=548%3A8288&PropertyCodeValue=548%3A8292&PropertyCodeValue=548%3A8289&PropertyCodeValue=548%3A8290&PropertyCodeValue=548%3A8287&PropertyCodeValue=548%3A8291&PropertyCodeValue=562%3A289196&PropertyCodeValue=562%3A289194&PropertyCodeValue=562%3A289195&PropertyCodeValue=562%3A292971&PropertyCodeValue=562%3A289189&PropertyCodeValue=562%3A289192&PropertyCodeValue=562%3A289193&PropertyCodeValue=562%3A289190
Pretty much everything on that list should be both well-made and fairly easy to build in. I'm a particular fan of the NZXT Source 210 for balancing both of those factors on a budget. And it comes in white - I think it looks pretty slick. The Source 220 and Merc Alpha are at least equally good, but they're both pretty standard black boxes. All of those are unfortunately full ATX cases...the only cheap micro-ATX I'd recommend to a new builder is the Fractal Design Core 1000, and I'm not 100% on that.
Also keep in mind that the price you're looking at on the Thermaltake is from Microcenter, which doesn't sell online and only exists in limited locations. If you aren't near a Microcenter, the Thermaltake will run you in the $45+ range.