What to do about outstanding subpoenas?

The Senate Judiciary Committee has threatened to subpoena Karl Rove for his role in the US Attorney firings that Attorney General Alberto Gonzales has been giving such shifty and uninformative testimony about and Secretary of State Condoleezza Rice has said she won't comply with the subpoena issued to her by the House Reform Committee. As Congress is covered under Article I of the Constitution and the presidency is under Article II, these two branches of our government are co-equal partners, but Congress is a "little bit more equal" than the presidency. As a military veteran, the way I'd put it is that the Executive Branch is being "insubordinate" towards the Legislative Branch, which generally results in what we refer to as "counseling". What's that you say? I might be angry because it doesn't look like the Legislative Branch will successfully end the Iraq War through legislative means? Let's just say that "counseling" has a wide variety of meanings. Granted, military superiors have strict limits on how mean they can be to subordinates, but they can have 'em hatin' life all the same.
So what can Congress do about Executive Branch personnel refusing to obey subpoenas? TPMMuckraker says that subpoenas are rarely followed through all the way to court and that they're usually either complied with or negotiated. What makes the difference between compliance and defiance? Public pressure!! We need to let our Congresscritters know that we're quite serious about wanting Executive Branch personnel to comply with their subpoenas, that we want to see Rove and Rice testify, under oath and in public.

Update: Very, very interesting. Seems the one thing that might make our President quit the game and leave Iraq might be an Iraqi failure to pass the Oil Law that the Bush Administration has been pushing for so long. "Bush warned al-Maliki that Washington expected to see 'tangible results quickly' on the oil bill and other legislation as the price for continued support." [snip] "Senior Kurdish lawmaker Mahmoud Othman confirmed that U.S. pressure was mounting, especially on the oil bill, which was endorsed by the Iraqi Cabinet three months ago but has yet to come to the floor of parliament."