Brian,
Setting a tripod on the same table works fine. If the table is big enough, you can do it with a regular tripod, as I did here:
So while I don't know what tripod you have now, you might not need another one to put in on the table.
How much money do you want to spend? Novoflex makes high-end equipment, and this rail is particularly expensive because it adjusts in both directions. While it would be nice to have this to make it easier to make small adjustments in position, you certainly don't need it. I have a single-direction rail that cost about 60% as much, but I did most of the table-top macro on my website with no rail at all. What you WILL need is a good tripod head.
And I know I am repeating myself, but you absolutely do not need a rail for stacking unless you go to a high level of magnification. I have never used my rail for that purpose. However, you may find it easier, in that it may be easier for you to control the adjustments between shots. If controlling that adjustment between shots is hard for you, a cheaper and easier alternative to an expensive focusing rail--since you will be shooting tethered-- might be Helicon Remote, if it will work with your camera and lens. You focus manually on the closest point and the farthest point, indicating each to the software, and then sit back and let it go.
Dan