Depends what you consider a fair bit of modding. In my opinion the only things you need to get high quality shots from a Gaggia are to adjust the OPV (dead simple) and install a PID (moderately involved). I’ve also added a dimmer switch for flow control and a pressure gauge on mine since both were incredibly easy. The Gagguino mod is more complicated than any of the above options since it requires soldering, but it lets you automate and profile all those variables. Either way, if you have the money and don’t mind spending it on a $1k machine then that would probably be the better option since you get a warranty and higher end components. But if you want similar functionality on a budget then you can’t beat ~$300 all-in for a used Gaggia and the basic mods.
As a fellow engineering guy I can definitely empathize! My previous (and first “real”) machine was a La Pavoni Europiccola, and I still have a Picopresso which I use for travel. Manual lever machines really give you an appreciation for the mechanics involved with making espresso. In the end the repeatability of a semi-auto machine won me over though :P