Upgrade Tank Size?

i currently have a 75g and im looking to upgrade. unfortunately i dont have the funds to buy new, so its craigslist and other forum searching for me. Originally i thought of going to 125g, i know i want 6ft instead of the 4 that i currently have. Others have said that the 18 inch depth of 125 is hard to work with, i currently have 18 inches to work with and its not ideal. so i know i want 6 ft long and at least 24 deep. dont really care about height as long as its at least 20 inches. So i think ive narrowed it down to 180-220g. unfortunately im finding it harder to find used set ups of 180-220 (that are RR) i dont want to have to drill or install an overflow box, im sure i would just mess it up. Im finding 125s all over the place. Am i overthinking the 125 to 180 difference? Any suggestions, thoughts, comments or used 180 -220 are welcome