Hi Hoyt.
I make video blogs for Gear-Vault.com and it's fun. I simply mic the cab with a SM57 to a small behringer mixer and run it out into the JVC HD MG-555 mic input.
Another thing you could do is video the amp and add a MP3 track over the video. I have not done this, but it is an option.
You can see my youtube videos here:
http://youtube.com/user/GearVault
(some videos are my customers playing the gear they purchased from me)
I would suggest making several videos. Video blogs need to be updated just like regular written blogs. I would have some videos with verbal demonstrations and all the other videos of playing.
I'd also suggest breaking the videos up. Like Make a 1 minute video of clean, then make a 1 minute video of crunch, another video of crunch with neck pick up, then heavy distortion video, and etc....
This will be easier for the listening if they are researching a particular tone clip, rather than listening through 8 minutes of playing of random tones. You'll also benefit because you are getting more videos 'out' there.
You might also want to make a video with short demos of 3 settings to sum up the amp for your website. This will be a teaser video to get the listener interested into clicking your youtube account to hear more Monster amp.
That's just my 2 cents. I'm sure other guys here will love to chime in for more insight.