You'll be looking long enough that you'll probably end up buying one new. I've been on the internet for about 12 years, and I've seen maybe a dozen and a half used Spolars come up for sale, and of those, only maybe 2 have been 4 gauge machines.
Make sure that you spend the money on the hydraulic system and you will be good to go for the next 30 years... Also, the Spolar wads are really nice to reload with... a little more money but well worth it. I am no longer a reloader machine mechanic. I reload about 7 times a year as it produces so many so fast that to get multiple flats of shells and store them is easy. I now worry about other things in my life, such as world peace and am I politically correct? Fred