Well, since nobody really provided you with a clear answer, I'll try to answer you myself.
The reason it displays two values is because the card underclocks to save energy; that's what they're talking about then they refer to Speedstep. From what it sounds like, you have it on some kind of dynamic switching of some sort, so it alternates the speed based on how much processing power the computer needs at any time.
What CHC does is give you greater control over the clocks; it'll allow you to undervolt as well as manage temperatures, batteries, and (if you have an ATI card) video overclocking. Really, its probably better than whatever Dell gives you, so I wouldn't be so hesitant to give it a try. I'll tell you right now, there's pretty much no chance of anything getting broken as a result. Besides, not only does undervolting not void your warranty, but it also increases battery life by a fair amount...
Also, as for the battery speeds... usually it clocks down REALLY low for this, usually speeds around 400mhz or so (unless you force it to do otherwise). Obviously, this is a big jump, but it does do a good job of conserving battery life.