I did just a few weeks ago and I love it!
I was able to get rid of a bunch of cables and HDMI adaptors and an HDMI signal switcher.
Being able to just use the HDMI inputs and outputs on the 976 makes life a lot simpler.
The 990 did have a OSD but you had to use an RCA video cable and I don't any of the newer projectors even have a composite video input.
I would not hesitate to do the upgrade!!!!
I am glad that I did for sure.
For $1K you can't do any better for sure.
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Epson 3500 3D projector
93" Carl's Place Flexiwhite DIY screen
Outlaw 976 Pre/Pro
Outlaw 7500 for LCR & L/R surrounds
1- Emotiva Mini X-A100 for rear surrounds
2- Outlaw LFM-1 EX subs
Oppo BDP-105 Blu-ray/DVD/SACD player
Outlaw LCR (Snell Labs) for center channel duty
Tekton Lore monitors L/R
4- Emotiva ERD-1s surround speakers
Monster HTS3600MKII power center