You can get a great power supply for about 100$ You can even get good ones for about 60ish or maybe some really good deals on them with some rebates. If you want a really nice one, most of the 200$ Antecs are awesome.
IMO, 2 things worth investing some money on if you plan to build you own PCs are a really good case (200$ish) and a really nice power supply (100$+). Mainly because if you get good ones, they are something that will last you for many many years and are the only 2 things that you very rarely have to upgrade. But, this is mainly if you are a PC buff and really want high quality. You can always get a junk case for 35$ that will do just fine, but IMO since it will last you for years, the high quality is worth the extra cash.
I highly recommend that before you buy anything, you check
www.newegg.com and look for quality products there. They don't always have to be the most expensive to be good. Just look for the items with the highest rating average and that have a high number of rates on them. If you see something with a 5 egg rating and 1000 people have rated it, you can bet that it is a really good buy. Read a few reviews too on each one you look at and they will tell you many good pros and cons.
Oh, and that thing you kept pasting shows a case that includes a power supply and then another power supply as well. You don't need 2 power supplies and so you could probably get a better deal on a case without a power supply included. Also, in most cases a really good 500W PS should do the trick. More isn't always better, but it probably doesn't hurt as long as it is from a good name brand.