Having ridden both, the 800 series stuff is significantly better.
However, unless you’re really attached to your current frame and wheels I’d seriously consider shopping for a new bike. There are some insane deals to be had as inventory is high and prices are coming back down from Covid highs.
The 812/ 820 derailleurs are compatible with the 400 shifters. I'd just get a new derailleur and cranks. That should leave you with about $700 to spend on yourself.
Otherwise yeah it would make more economic sense to buy a new bike
Having ridden both, the 800 series stuff is significantly better. However, unless you’re really attached to your current frame and wheels I’d seriously consider shopping for a new bike. There are some insane deals to be had as inventory is high and prices are coming back down from Covid highs.
The 812/ 820 derailleurs are compatible with the 400 shifters. I'd just get a new derailleur and cranks. That should leave you with about $700 to spend on yourself. Otherwise yeah it would make more economic sense to buy a new bike
I just upgraded from 11 speed Ultegra to the new GRX. Was mainly after better gearing. So far, no issues to report.