Wow, thanks everybody for all the replies. I know once the upgrade bug kicks in it's hard to shake. I'm the same way with other hobbies and interests so I know it's a matter of time before I'll eventually get something to replace the Gaggia. But I am having fun tinkering with the GCP and seeing what these grinders can do for its espresso quality.

I recently saw this guy compare the GCP with a Linea Mini and was surprised at his admittance. Maybe every espresso machine has one good shot in it but the higher caliber machines do it more consistently. Before I make any judgements on getting another machine I'm going to try a 6 bar spring and a VST basket to see what they do.

I believe the classic response to a cheaper machine versus an expensive one, is that yes they both will give you acceptable espresso, a manual machine can do that, my 9barista can do that, the key difference appears to be more consistency and convenience/enjoyment from the more expensive machines as they naturally contain more technology and quality that removes uncertainties that may cause frustrations, e.g. PID's, dual boilers, steaming power etc. The rest is just about design aesthetics, workflow, footprint, brand, all the usual variables that affects other hobbies also. As already said, if you enjoy yourself and get espresso out that you like, then you can't ask for more.

Felt like posting an update here since several people recommended the Cafelat Robot as an upgrade to my GCP. I have indeed purchased and received a Robot and all I can say is THANK YOU to those who mentioned it. I have not had a single thought about going back to my modded GCP as the Robot is just absolutely wonderful in making delicious espresso.

Honestly, after my second shot ever pulled on the Robot I experienced the best shot I've had to date. Wonderful texture, balanced, and smooth. It has definitely quashed any desire to spend any more money on a much more expensive espresso machine for the foreseeable future.

The only downside is I'm having to buy more beans as my wife has now realized how great straight espresso can be and demands two shots every morning.