The 890 series are nice routers, I have 2 of them. The Fixed base works great in a table, even without the above the table height adjustment. On one of my router mounting plates I didn't drill the holes for the height adjuster, but it's fast and easy from under the table as well. Plus, I'm always 'eyeballing' the height from the edge of the table anyway, so I'm right there at the adjuster.
Looking at your hole patterns in the top of your table, you're going to have to drill at least one new mounting hole, and 2 holes if you are going to use the above the table height adjuster.
You can usually find deals on the 890 series most anywhere, I got one of mine from Amazon, the otherone used from Craigslist.com. If you go with the single base one, you can usually find a plunge base for sale on ebay, or pick one up from Amazon or potercable.
Hope this helps,