In some ways there is no equivalent body in Canon's lineup, especially if you emphasize the word current. The last APS-C camera Canon has released in the range above the Rebel series is the 60D in mid-2010. The 30D through 50D were a logical evolution of the x0D line. With the introduction of the 7D and the 60D, Canon created two tiers that occupy a space just above (7D) and just below (60D) the 50D they replaced.
What will be the logical successor to your 20D depends a great deal on what features and qualities of the 20D are most important to you.
Image Quality All current Canon APS-C bodies use a version of the 18MP sensor that first appeared on the 7D in 2009, which dwarfs the 8.2MP of the 20D. They do so at the cost of much smaller pixels (4.3µm vs. 6.8µm). Advances in processing algorithms have allowed Canon to maintain or slightly improve things like low light and high ISO/low noise performance even with the smaller pixel size. Any of the current APS-C should provide better image quality than the 20D, but if you want the advantage of larger pixels, you'll need to consider a jump to Full Frame cameras such as the 6D, which is Canon's first "mid-range" camera with a FF sensor. Of course that would mean any EF-S lenses you own would need to be replaced by EF lenses for the 6D.
Speed/Handling If the way the 20D handles is important to you then the Rebels which lack the second control dial on the back are eliminated. Ditto if you want a true pentaprism viewfinder instead of a pentamirror. The 5 fps of your 20D is matched or exceeded by the Rebel T5i (5), 60D (5.3), and 7D (8.0). The aforementioned FF 6D just misses the mark at 4.5 fps. In terms of buffer depth none of the current models are slower than your 20D at 23 jpeg and 6 RAW files. The Rebels can burst for anywhere from 22 to 34 jpegs and 6 RAW files before the buffer is full, the 60D goes 58/16, the 6D goes 73/14 (125/17 with an UHS-1 compliant SD card), and the 7D with ver.2.x firmware can take 130 jpeg/25 RAW in a single burst with a UDMA-7 CF card.
Durability Your 20D had a magnesium allow body and a shutter rated for 50K actuations. The only APS-C body with a magnesium frame is the 7D, which is rated for 150K shutter actuations. The 60D is made of aluminum and high grade engineering composites/plastics with a shutter rating of 100K. The Rebels, made of composites/plastics are no longer rated in terms of shutter durability. The 6D has a chassis much like the 60D and a magnesium polycarbonate resin exterior.
Since your question sounds like you are still happy with your 20D at present, you might be better served to wait a few more months before replacing it. The replacement for the 60D is expected sometime this year, as is a possible replacement for the 7D later in the year. Both are long overdue.