I wouldn't mess around with a HotPlate or a Weber. You want a attenuator because you want to turn up your amp to hear it the way it is designed to be heard, but at more reasonable volumes, right? These power soaks will not do the trick, and in the end I doubt they'll leave you feeling satisfied. I have done copious amounts of research to achieve this very thing. My conclusions? You really have two options. First option, get an ISO box. Are they perfect? Absolutely not. Yet, are they getting better? They sure seem to be with the release of the Rivera Silent Sister. I have one that is due to arrive at my house on Tuesday. I will gladly post clips on here for your enjoyment. From the previous clips I've heard they sound absolutely fantastic! The following is Zorran's clip of the Silent Sister and his Mark IV. Absolutely brutal and awesome! If you have a PA, then this would be a good possibility -- especially at gigs. This runs $999.
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=147856&songID=7351450
If this doesn't float your boat, then check out the Faustine Phantom DX ($800) or the Aracom ( $650 - $770) attenuators. Those two are hands down, the best innovations for attenuators today. Both websites have clips galore showing off what they can do. I was going to go this route, but I really like what the Silent Sister has to offer. Time will tell of course, but so far from what I've heard, I am sold on its potential.
Also, if you plan on ordering the Faustine, you'll have to wait 6 months. I called the other day, and that is the time I was given. They are just swamped with orders. The Aracom is a bit more reasonable, with a 5 week wait list. Both of these have wait lists for a reason -- they are that f-ing good!
HotPlates are great when you aren't trying to attenuate high gain, high power amps IMO.