Dear Calamity,
First off the Tarmac. You need to see how much wall you wish to open up. If your system is on one zone, then you need to isolate the first from the second floor. This you can do by installing a chase to the second floor. Make one circuit and drop down to the basement. Isolate the first floor and install a second zone valve. You will have two thermostats to deal with at this point. Locate a qualified Hydronic Heating contractor, as this type of endeavor is best accomplished by a proffesional. There are too many varibiles to contemplate in your situation. If I am not physically there to see your system, I can not accuratley define your problem.
Len

As usual, good advice from Len the "Iceman" or should it be "Heatman"?

Hydronic problems can seem overwhelming, but not for a professional.

If your boiler is sized correctly, and will handle the heat load, then it's just a matter of re-routing (read controlling) where the hot water goes, and when.

I have learned more than I will ever use, at www.heatinghelp.com Please ask your questions at "The Wall" then type in your Zip code at "Find a Contractor" and you will get all the help you need.

Heatinghelp is a lot like Bob's place, very friendly folk who give the best advice for free (not work )

Also visit Harold's place at Hydronic.net I think. Harold's site is a mine of information, as is he himself.

Good luck, and yes, God Bless America and you all.

Brian in Swampland (Louisiana, where it's as cold as the Noth Pole right now)