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

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

Georgehifi, ground clamps on water pipes are frowned upon in the NEC

We use both, earth spikes and the water pipe, if you have good salinated ground earth spikes work a treat, but if it's not, then the backup water-pipe is great to have also.

Cheers George 

All is useless to do inside the house if the connections to the house barge board and to the street power pole is old and hasn’t been cleaned and tightened in decades.
https://checkthishouse.com/wp-content/uploads/electrical-service-connection-at-the-house-wall-is-too...
These connections can be under ground if a newer (20yold) development area.
 https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSku4mCRiijbZCgGQkLvqpet38UA9-8t-zZEFuaGMTTApbU... 

Cheers George

In Australia I would ask for quality 20A cable to be used, also get him to use high quality ac power points, and use dedicated very good HQ circuit breakers in the service box.
 Also if he's licensed for it, get him to tighten all connections (neutral active and earths) check the earth on the water pipe, add an earth spike if he can also , all connections in the service box on both sides of the of the metering unit, also outside on the barge board of the house, and if he's able, on the street power pole that brings in to the house barge board.

Cheers George