I have a $20 drill from Canadian Tire that will punch holes through any PC case built since 1990, not sure about that 1970-1980 steal though ;) If you purchase a hole saw your also going to need the hole saw arbor and it's a few extra $ on top of the saw itself. Also you should pick up a punch, you use it to tap a small recess in the middle of where you want to drill so your drill doesn't skip or slid across your pc case. there cheap and will save you some problems so get one.
You'll have to contact them to see if all you need is the saw and arbor, my arbor has an attachment that fits into the saws to keep them from rotating and that arbor looks different. I've purchased lots of stuff from Bosstools, there a great store with good service.
without indicating what size hole(s) you want to bore no one answer is going to fit.
You can get both very cheap hole saws and drills. If you want to drill 3 1" holes a $2.00 saw and a $20.00 drill will do the trick.
Professional tools will perform much better - the hole saws will maintain a decent cutting edge, cut smooth accurate holes and the drill will last for years. Larger holes using professional hole saws use a 7/16" hex shank which requires a 1/2" drill chuck. A 3/8" chuck will be too small.
I've purchased lots of stuff from Bosstools, there a great store with good service.
I bought a Milwaukee 14.4v Cordless Drill from them and got jacked around for weeks where I was forced to call repeatedly to make inquiries, lied to on 2 occasions and FINALLY got the drill. Never again for me ...