Okay, the first thing to do is to disable all the the programs which are starting at boot that you don't actually need. Google it: there's lots of tutorials, and it should really help with boot speed.
Secondly: defragment the hard drive. Just search Disk Defragmenter in Windows and let it do it's thing. That'll help general loading times.
Thirdly: Old drives are simply slower because they run at lower rotational speed and have lower storage density (in terms of GB/platter). 
I actually don't recommend spending extra on a WD Black--most of that money is because of the longer warranty. Go with a 7200RPM single platter 1TB drive instead, like the the newest Seagates (model ST1000DM003). The SSD, on the other hand, is a good idea. Just don't get carried away with the IOPS stats and so on; cheaper drives like the Samsung 840 non-Pro, Crucial M4, Plextor M5S, and Sandisk Ultra Plus are all perfectly good, and not noticeably slower than the top end drives for consumers.