The best think tank on this issue, bar none, is Center for Immigration Studies, a group whose research on the impact of illegal aliens on our economy are the gold standard.
If we legalized the current populus of illegal aliens and combined that with new, tougher border control legeslation, that would be the best of both worlds.
By tough, I mean machine-guns lining the border tough. That's the only way to stop people from crossing. Putting them in a truck and taking them back isn't going to change anything, and putting them in prison just sucks up more tax money.
Legalize the ones that work hard and have lived in the country for a long time, and kick the rest out. Then line the border with machine guns and the problem's solved. ;)