you can do a search for those parameters under resources--diamond search. it's hard to answer questions like 'what is the cheapest' because if you do a search some of the diamonds are certified by different labs so you are not comparing apples to apples. in general the sites that do not provide services such as photos/idealscope photos are going to be cheaper.
just as an example I ran a search, and a
1.70 carat I VS2 EGL diamond is ~$6000
but 1.70 carat I VS2 GIA diamonds are around 11,000.
The cheapest prices come from people who are lying about the grading. Cheaper still, I suppose, is from people who don't actually deliver merchandise at all.
In all seriousness, read through the tutorials a bit and pay special attention to the parts about grading, grading reliability and the various scales that get used. VS stones vary by more than just price and sometimes I means K. Your question tells me that you are heading a path that's sure trouble.
here is a link to a search that I did with 11,000 max budget looking for I, VS2/SI1 diamonds (GiA or AGS, VG or better polish/symm, excellent cut on HCA)