Solidworks, thanks for taking the time to help.
The rendering in solidworks can utilise more cores and also some add-ons like photoview 360 , 8 cores would be easily achievable in that budget.From what I've read - I don't use it myself - Solidworks itself is largely single-threaded but Solidworks Visualise likes a quad core CPU. So if you want your single core to go as fast as possible for as long as possible I think you will be well advised to get as good a CPU cooler as possible. The gold standard is the Noctua DH series.