Bill, it sounds like you are building the ultimate high end 75 set. It appears that you have set some strong expectations of what type of cards you want in your set...which is good.
Having built both a high end raw 75 set, followed by a PSA 8+ set (
http://www.psacard.com/PSASETREGISTR...et.aspx?s=3545 ), I could recommend the approaches I took.
With the raw set, I looked for a raw lot/starter set of commons in high end shape. Ten+ years ago this was an easier find than today. This got me most of the way, minus stars and some of the other key cards. I picked up some raw stars at shows, but found the graded cards of stars were plentiful and eventually completed the raw set with some PSA stars (8+). However, a third of the set was in EX-MT to NM shape or off-centered, and like you, I wanted a NM-MT set that was centered. I found it cheaper at this point to buy several other high end 75 sets, go through the each of the newly purchased sets and upgrade my set. This upgrading was actually the funnest part of building this (or any) set. Eventually I was satisfied with my mainly raw set. The extra raw sets I then sold off one by one, and in most cases at least covered my costs.
The PSA stars I had picked up for my mainly raw set were nice and gave me a decent start on a full PSA set, so I decided to start the PSA set. I picked up a starter lot off of the CU BST, worked a few additional trades, and suddenly I was half complete. 4SC and other ebay sellers helped me complete it. I sold off my raw commons to cover a small portion of the cost of the PSA set, but a decent portion of the cost had long since been covered as I had many of the stars already in PSA form from my raw set.
My recommendation if you chose to build a raw set would be to either buy multiple raw sets, pick out the upgrades for your set, then resell the sets (maybe through an ebay consignor), OR buy the raw cards in person (shops/shows). Trying to buy high end single commons, such as the one's you are seeking for your set, online can be a very frustrating venture.
Obviously more costly and time consuming than a raw set, the 75 PSA set is one of the easier PSA sets to build.