You can use Advanced Auction House addon to increase the possibilities of filtering.
For example you can filter by stat values in this addon, so you won't get 500 manastones, but only the stones with the values you set in the filters.
You can put more filters one your search using AAH, no doubt about that.
The thing is, it's still limited to 500 results server-side and the AAH-specific filters only apply into the results the client gets submitted by the server. (So you still don't get to search more than 500 at once)
Having mentioned that I think a goal could be to make the server-side filters more specific, so there would'nt even be 500 search results to be submitted.
A pretty good option is imo doing a price range (like already mentioned) if thats is possible to implement.
I don't know how much workload this would put onto the server compared to just submittung the results currently allowed for the server-side filters or if it's even possible since I don't have the chance to test this, but I think it would be worth to look into.
Regards, Saphira
