Best bang for the buck: p.stage, cart. or stylus?

In preparing to move overseas, and not being able to take my record collection with me, I'm planning to spend the summer recording as many as possible to digital files. My current system is quite modest: a Pro-Ject Debut III turntable with the Ortofon OM 5E cartridge it came with, running through the phono stage of a 10 year old Marantz receiver. (Alas, I can't take my Triangle Antal speakers with me either!) They've served me well enough, but I'd like to get the best quality recordings I can. I'm on a very small budget, but I'd consider upgrading something in this system. If the phono stage is the best place to make the upgrade, then I'm looking for something that I can reasonably expect to resell within $150 of where I bought it at the end of the summer. (I was looking at the Graham Slee 2 SE). The other recommendation I had received was the Ortofon 20 Stylus in place of the 10 that I have now.
Both your cartridge and your phono stage are basic models. You could very profitably improve them both. If it were me, I'd start as close to the source as I could. You're not going to change the arm or the TT, so the stylus is next.

However if it were me and I were going Ortofon I'd pay the premium for the fineline diamond on the Ortofon 30. Next would be the phono stage, and the Graham Slee is a good budget choice.