My New Magnepan 1.7i's sound dull and lifeless on the top end...why?

I hate to say it because I'm a Prima Luna fan (have an EL34/KT88 integrated). But they don't extend as well as a good SS amp. Gold Lyon KT88s helped but switching to SS works better. 
Make your room more lively, put KT88s in you amp and that is the best you can do. To tell you the truth Maggie 1.7s don't have the best tweeter, you'll need 3.7s for that but you can get them to work reasonably well.  

@nayles02

Strip out the Anti Cables speaker cables and try running just the panels alone with any decent speaker wire that you have to hand...
If that improves matters try replacing the IC’s as well...

A cursory glance shows the amp has what - 8, 4, 2 Ohm outputs. If you're on 8 Ohm, try the others. 

Thank you for the responses. 
- Using an EQ does help, but introduces it's own set of undesirealbe sonic characteristics.
- I would hope my Pass Labs gear would be considered good SS...yet still unacceptable in the high frequencies, and only marginally better than the Prima Luna gear on the 1.7i's.
- I have a pair of LRS's who's high frequencies are vastly superior to the 1.7i's??
- Swapped out the AntiCables with some Canare interconnects and Mogami speaker cables...sounded worse.
- I've tried all the settings variations on the PrimaLuna's 8, 4, and 2 ohm, and high & low bias.

The funny/bonus thing is the harsh poorly recorded music sounds better than any of my reference audiophile recordings on the 1.7i's. I may keep them just for that gem of an attribute.

Have you tried using the stock u-shaped jumper in place of your anticables attenuator? Seems a likely culprit....