Stereo- WS Syn 2 Amp tuning HELP

What is the best way to get the gain set "perfect" on the new Syn2 I just added to the system?
Existing system had,Kenwood head unit.Audison Srx 5.1 amp running Arc Audio sub and 8 speakers, all Wetsounds,6.5's inrterior,Pro60's on tower. Instal was professionaly done by Scream Marine in Dallas TX. So all tuning done by them. I wanted more power to tower speakers so adding the Syn2. All speaker loads at amps are 2ohm. What is the best way to get the gain set perfect on the towers before mount complete because very difficult to get to settings where it's mounted at. Have crossover set for the Pro 60's at 100Hz /high pass per recommendation from Wetsounds, any input on that as well? Thanks

Amp is still not mounted yet,still time for the guru's in the crowd chime in. 700w to the 4 Pro60's is just what the doctor ordered. Way more dynamic sound when you have the power to drive them the way they want. Very impressed,very happy. Still lookin for some advise on the gain setting, knowing it's subjective to the system ect... just curious what others have done to get matched for best results.

The way to get it perfect is with an oscilloscope. Without an oscilloscope I like "Method 2" on this page for the full range channels:
http://www.thesuicidaleggroll.com/gain.htm

Got it. Spoke with the "G" man, got it all dialed in and it's great. (Thanks Grant, good speaking with ya) Wattage is a beautiful thing