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

The crossover in the 1.7i is pure junk. Replace the capacitors and the inductor, ditch the stock  wiring. Lose the fuse
And you  will have dynamic range coming out of those speakers that you  would not believe. 
I am saying this, because I have a pair myself, and did all the upgrades. 

Absolutely @yuviarora, the binding posts as well (Cardas posts will fit right in the stock holes). That whole plate is filled with ferrous parts! Have you watched the GR Research YouTube video in which Danny Richie measures the 1.7 and looks into it's x/o? Well worth your time. A YouTube search for "GR Research" will bring up all Danny's videos.

@bdp24 I haven’t watched that video, but I will. The post was the 1st thing I chucked, now my crossover is soldered onto my cables directly.
I have Mundorf Evo Supreme oils for the mids, Mundorf Supreme Silver oil for the Tweeter, Jantzen wax 12 gauge Coil inductor for the Bass, Neotech 14 gauge Solid OCC Copper for the internal wiring.... The speakers sound incredible, Jazz is just to die for.
One of the coolest surprises was Electronic music, which previously sounded like monkeys beating pots and pans on the speakers, is now one of the most detailed, crisp 3 dimensional sound I have heard on any speakers.
My friends call the Maggies "The Spaceship". EDM sounds like a mushroom trip, no distortion whatsoever.
Fantastic speakers, but the crossover upgrade is an absolute must in my opinion.

@yuviarora did you install the GR-Research Maggie upgrade or are the parts you mentioned above something you selected yourself, or was your upgrade obtained from someplace other than GR-Research and if so, where? I have a pair of 1.7i. Thanks!

@kingbarbuda I made the crossover myself, just upgraded the factory crossover, kept the values exactly the same.
You need 115.8uf total for the mid section (3x33uf+10uf+6.8uf), 10uf for the tweeter, and a 1.4mh inductor for the bass panel.
If you follow the existing layout, you can just build a crossover using the same layout. A schematic is also available online.
I had to build a box attached to the speakers in the back of the panel, I put my crossover inside it. You can go about doing it however you see fit.
I went with mundorfs because they are very highly rated boutique parts, build it well and build it once.
Changing the crossover is an absolute must on these speakers.

P.S. Just  watched GR research's video, and his  way of building the crossover is his own, but I can tell you this, the stock configuration after changing all the parts is not lacking in the least. Treble is beautiful, shimmers that are incredibly detailed and never harsh. Everything is in balance.