Don't limit yourself to the 870 HD.
The HD is just an 870 Express set up a certain way. This is called 'marketing,' or 'how to soak the buyer.' There are lots of Expresses out there that could meet your criteria that are not labeled 'HD.'
Any short-bbled Express with a cylinder bore will work just fine. How short? Look at and handle the shotgun...if it seems short and handy, it will work. At the ranges we're discussing, length of barrel will not matter much. Type of choke won't matter too much either for shot, but if you want to shoot slugs, stick to mod or cyl (this will be stamped on the barrel. If its not, ask).
If you can find a used Wingmaster for a good price, consider it. Its the same gun, just prettier. the Express is the 'economy' model, but the difference is in appearance, not anything that matters. And frankly, the matte finish of the Express is (IMO) easier to maintain and far more practical. Its also way cheaper.
Mike
PS Express vs Express Magnum: most of the ones you'll find are actually Express Magnums. This just means its set up for 3" shells. Non-magnums are limited to 2 3/4" If you get a good deal on a plain express, don't pass it up. 2 3/4" will kill things dead. The added flexibility of the 3" chamber is nice (thats why the vast majority are Express Magnums), but not absolutely required.