Pardon my ignorance, but it's been 20 years since I last had a chance to enjoy my times with my loyal A500 before I sold it, is this the
DENEB USB 2.0 CONTROLLER you are all talking about?:
http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=795
Are there any other alternatives to add a modem and USB connectivity to my "new" A3000?
You can add a PCI bussboard which will give you access to USB.
You could also add something with a clockport (like X-Surf) and add a subway to that, but subways are getting hard to find as well and will be slower than a denab.