As e61 HXs go, your Astra Pro is a very competent machine that is very short on extra features, convenience options, and nice little details. My memory of the two that I have had around my bench are that they are well/over built where it matters most and that's about it. If you upgrade to a more refined e61 HX, you'll be paying for feature and not for improved taste. That being said, there are a lot of really mature e61 HX machines out there that offer a lot more comfort than your pro does. I personally value being able to plumb a machine into a filtration system because that's easier than balancing your water tank by tank, and a good drip tray/grate design (that recessed half moon tray on your pro is the weakest tray solution that I have seen so far). On the flip side, your steam valve has the best action short of the big knobs on LM Lineas and GB5s - I love knobs and really don't like the little joy sticks.
The one big shot quality difference will be the ability to add an Erics Thermometer, which will really improve your first shot and shot-to-shot consistency. Then again, I think Astras proprietary e61 style group is heavier that a traditional e61, I think by almost 1lb of brass.
russel at anacidicandbitterbeverage dot com