One of my past favorites for closeups was a 300mm f/4 IS lens with a 1.4X extender. I also used a Canon 500D closeup filter on the 300mm lens without the extender.
I no longer have the 300mm lens but I have the 500D filter and a 1.4X extender. The longest lens I currently own is a 70-200mm f/2.8L lens without image stabilization.
One of the problems with using the 500D filter is that there is a very limited in focus range. Using it with a zoom lens creates more options than with a prime lens however.
Here are a bunch of samples. From the 100mm macro at minimum focusing distance to various zoom shots with the closeup filter, with and without the extender.
|100mm macro lens at minimum focusing distance (MFD)
|70-200 zoom at 200mm w/500D w/o extender at MFD
|70-200 with extender at 140mm w/500D at MFD
|70-200 with extender at 140mm w/500D at Infinity Focus
|70-200 with extender at 280mm w/500D at MFD
|70-200 with extender at 280mm w/500D at Infinity Focus
Another closeup option is the crop sensor SL1 and the EF-S 55-250mm lens which focuses pretty close.
|55-250 at 250mm (400mm EQ) at MFD (33.46" from sensor to subject)