Well after a week with the TH700 I returned it. Although at first I thought I liked it because I could feel the difference in power, doing a side by side comparison with the TH500 with different cabs I found the TH500 to sound better. Best I can describe it is the tone of the TH500 sounds more broad and full where I found the TH700 tone to be narrow and thinner that the TH500. Although the initial impression was they sounded very similar, no matter how much I tried I could not get the TH700 to sound the same as the TH500. The TH700 may be for some, but for me I prefer the sound of the TH500.
I'd try another or talk to Aguilar to see if there was something funky with the one you got. When I A/B'd the 500 and the 700 they sounded pretty identical at lower volumes. When I pushed them you could tell where the 500 ran out of gas and the 700 kept humming along. IME the 700 is just more of a great thing! If the 500 fills your needs then your all good but it's strange that you'd find that much difference between the two.