afx,
I can't tell you what is the most cost effective for you in particular but I do have some feedback.
I do this professionally. I have a Epson V800 flatbed and a Nikon Cool Scan V (no longer produced by Nikon). I control the scanners with Silverfast Studio 8. All of this "stuff" cost a lot of money, unfortunately. After scanning thousands of slides, I have chosen to use the humble Cool Scan. I choose to put the effort at the scanning part of the process because, in the long run, it saves time. One slide at a time, where I can adjust the input curves and select how to use all of the capabilities of Silverfast. The IR feature of Digital Ice, is the single most powerful tool in arsenal. The Coolscan device also has a autofocus feature which is most useful since the file often is cupped. I brush each slide before each one is scanned. But even with that you simply cannot get all the dust off, not to mention other detritus and scratches. The IR scan is simple a miracle!!! Silverfast has all sorts of nice features, to adjust the exposure range, control the input curve, adjust for underexposed slides, adjust global color correction, etc. I choose to do the work up front because that is less time consuming than doing it in post processing.
Without a doubt, Digital ICE, when implemented properly, is the "Magic" which saves an incredible amount of PP time.
Doesn't solve your problem, but hopefully useful to you.
Lowell