Going to have a dedicated line installed- What should i know to ask for?

Here is a tip: plant corn early. 

This might take some time but there are a few members here who are steeped in this, with one or two in the extreme and they may not see this as I haven't seen them post in awhile.

Having said that, do a search on "dedicated lines" and you'll see lots of discussion on it. It will take time but the few I mentioned will pop up repeatedly and you can zero in on their thoughts and maybe PM them with your particulars.

I can't, for the life of me, remember their names.

All the best,
Nonoise

This is a commercial HUGE building in Brooklyn. Aside form street power there is a lot going on in the building itself... It is my thinking that a dedicated line with proper ground would still be beneficial. He is charging me $300 per line... Not sure i have anything to lose...

Just want to get as many tips.

Well your at the mercy of the buildings wiring. Yes do what you are going to do.

For all your line level equipment, I suggest to use a 110v to 110v isolation transformer. Something like this. And if you use them, plug your mains filter distribution board into the isolation transformer, and your line level gear into the board.
http://www.bkprecision.com/products/power-supplies/1604A-single-output-isolation-transformer.html

For your power amp/s, plug direct into the new dedicated heavy duty wall outlet. (NO power conditioners, they sap the dynamics.)

Cheers George

The NEC is the National Electrical Code in the U.S. Covers every state. Personally, I’d run 12 wire for 20amps, rather than 14, there’s virtually no difference in the price of the material, compared to the job as a whole. Beyond that, I’ve no idea about audiophile grade connections, etc. Do your research ahead of time, or let the electrician know your plans/wishes before he’s on site, not after.This all presumes that it’s even possible to install a dedicated circuit in an old building like you describe. You may be downstream of other sub-panels, and the like. Georgehifi, ground clamps on water pipes are frowned upon in the NEC, have been for years, even though thousands still exist. Anything new almost always gets modern 10’ ground rods driven into the earth, and in pairs. Too much old iron plumbing has been replaced in pieces with plastic, disconnecting the electrical grounds. You may already know this, of course. Also, at least in the part of the U.S. that I'm familiar with, electricians don't work on any part of the service upstream of the meter, such as the "drops". Those are done by the local utility district. And as a disclaimer, I’m not an electrician. Good luck.

I think one member is jea48, and it looks like builder3 may be, not sure about that.