What year is Your Glide Bro?
The new SD 800.4 amps are nice and small with the same power, if not more, like the originals, I believe.
I have a 2012 Custom and have 2 of the original 800.4's mounted between each glove box and inner fairing.
The newer versions would fit much better.
If You have a Rushmore Glide I would definitely go for the newer version as the space in the fairing is less than a Pre Rushmore. If it's 2013 and down You may find a great deal for an original SD 800.4 and save some cash.
Either way, You won't go wrong with Soundigital.
Hope this helps.
Mike U.