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The main difference between Achros and APO scopes is the focus of the different wavelengths of light, in an APO the visual colors focus pretty much together for practical purposes, this is done by using glass with varying refractive properties which unfortunately tend to cost more. In an Achro for most uses its not so noticeable but the wavelengths don't converge at the focus point quite so well, this usually shows itself in the blue end of the spectrum, as a result it's not so focused, and just as you defocus a star it spreads wider, but in this case only the blue, the end result is blue halos around the brighter stars, it's there on all the stars to some extent, your big bright stars really show it up.
So is it usefull for astrophotography, yes, but with caveats..... If you are using a narrowband filter then converging of different wavelengths is not a concern, if you are using a RGB filter wheel focus for each color separately, in a OSC you will need to photoshop out the halos to some degree.
As in all things in life you tend to get what you pay for, a more expensive scope should apart from APO also have a better focuser, better baffling etc etc.
Commonly it is considered that the mount is where the dollars go first, as with a good mount your stars will not show poor tracking ( provided its aligned etc), if you have a poor mount it doesn't matter how good a scope is you have stars wil be eggy or worse.
If experience is anything to go by, most people buy and sell scopes several times, so regardless of what you buy now, you will at some stage upgrade it. There's no perfect answer, it comes down to your budget.
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