Are you saying that that you want to go with both an IPS and a TN panel at the same time? I'll be honest, after using the IPS panel..it seems quite unlikely that you would want to drag something over to the TN panel. But I do realize that going with a dual IPS solution is extremely costly.
What you might consider doing is splitting the difference and getting 2 of the Dell U2311H monitors instead. These are the lower priced Dell IPS flat panels. They are about $300 for a 23" display. So, 2 of them would cost you $600 and get you consistent imaging between the 2 in a dual monitor setup. While not as nice as the U2410...the U2311H is going to be better than the TN flat panels.
Here is a review that covers that monitor Dell U2311H review - FlatpanelsHD