Is there any way to enhance the heat without changing the taste in a hot sauce?
There are a few things that might work. I would probably just add more seeds. The majority of the capsaicin where the heat comes from is in the seeds, while the majority of the flavor is in the flesh. You could just add some seeds from a hot pepper like habanero or cayenne or even more jalapeno seeds. 

You could also add some chili pepper that has heat but not a lot of flavor. Some examples include cayenne and chile de arbol. Thai bird and african bird chiles are hot and also don't have a ton of flavor in my opinion. 

Another option is to try a chili extract. For example, a habenero extract will have some flavor, but a small amount will add an enormous amount of heat. So you may be able to get away with an amount small enough not to add much flavor, while at the same time kicking up your heat to the desired level.

Personally I like habenero, esp in El Yucateco sauce, which I often add straight to hot sauces.