I believe arimidex is good and is often used for on-cycle estrogen control. However, I believe that suicidal AI's like aromasin are preferable during PCT. The goal during PCT should be to normalize your hormones, so sending your estrogen crashing to almost nothing with arimidex or letrozole is a bad idea. Currently, I am using a combination of nolva/clomid/aromasin. I too used Test cyp for 10 weeks, and it made me crash and caused some testicular atrophy. So, I used HCG at doses between 250 and 500 IU's every 3 days for 6 doses total. People often recommend much higher doses. But, I personally am very sensitive to HCG and higher doses cause my estrogen to get out of control.
I am taking 25 mg of aromasin daily, and it has just moved my estrogen into the lower/mid range of the normal range.
Before you start a cycle, you should make a PCT plan, and have all of the drugs you could ever possibly need. For example, I have HCG, clomid, nolva, aromasin, arimidex, letrozole, Animal Stak, and Androbolix. Of course, I'm not using all of these, but I have them available. In addition, it is wise to get tests and adjust the strength of your PCT based on those results as well. based on how you feel. It often takes several weeks to get prescription drugs like nolva, so you need to be prepared before hand.