Upgrading from T450. What should I look into?

Hi guys, been with my t450 for years now and I love the thinghave dissasembled and upgraded everything that I could on it and while it runs solid, its technically my works and Id like a personal laptop I can tinker with as they might want it back someday (though i doubt it). Any recommendations onanother thinkpad to upgrade to? Bonis if I can make a project out of it and seap out some parts to make it even nicer (thinking about upgrading the a screen on the t450 if I don't trade up). Been looking at the t550 but I'm not sure I've only really messed with the t450 and t450s.

Edit: cheaper is better and I'm down to upgrade slowly over time. Max could drop like 300 out the gate but that'd be pushing it a bit.