What easy and cheap upgrades can I make to my shimano 600 EX drivetrain (6 speed arabesque)? Id like to keep the front and rear derailleur as I really like the engravings, and upgrade to bar end shifters. Is it possible for me to upgrade to 7 speed with the same derailleur? What about indexing with bar ends? Hyperglide? Thanks!

You can do everything you want with the same derailleur (7 speed, bar end shifters, hyperglide cassettte), except for the indexing. If you want (reliable) indexing, you will need to upgrade the rear derailleur to an SIS model.

If you're willing to stick with friction shifting, find an era-appropriate pair of suntour bar ends with micro-ratcheting action. They'll be like heaven on the end of your handlebars.

^What he said, just make sure that your frame spacing works with a 7 speed freewheel.

Should I go used, or whats the cheapest way to do this? Id like to stay reaaaal cheap, but bar ends seem to be pretty expensive

If you want to go barends, and can live without indexing, here's what I did with a set of $30 Riv. pods.
I used Shimano Light Action DT levers. Mounting required grinding off the stops on the back side of the levers and addition of a 3/8 spacing washer for cable alignment. Pretty sure you would be able to get the Arabesque levers to work and I bet they'd look great.

Hmm. I have a set of the SIS/friction shifters at home that has a clamp-on band, and uses the dreaded Shimano standard -- don't know if they'd fit on Shimano braze-ons (knowing Shimano, probably a different "standard!") I'll check when I get home, if I can remember that far back by then.

Im fine with just friction, Im trying to upgrade the bike so that itll be a good tourer. The only other thing Im worried about is the double upfront instead of a triple, but I think I can live with that. I dont have DT shifters right now ( have some clamp on ones onto the stem, which are actually kinda convenient).