I am not a fan of the Aguilar line of products either. I also am not a GK guy. Not saying that there is anything wrong with either brand, they just don't work for me.
I played Ampeg SVT-CL's for decades and then went to the Ampeg V4B to shed some weight. Around 2000 I went to Ashdown's ABM 500 series for about a decade and loved it.
When Mesa dropped the Subway line I started out with the D800+ and it met every need I could possibly have. It can get really close to the Ampeg vibe as well as Ashdown. I also tried out the WD800 and it was a killer amp but I preferred the D800+. When the TT800 came out I was GAS'ing hard and tried it out but IMO at that time I preferred the D800+. The D800+ was my main amp for many years and then recently I went back and tried the TT800 again and absolutely loved it this time around so, it has been my primary for the past year.
I still own the SVT-CL, V4B, Ashdown ABM 500 and the D800+ but they stay in my studio.
The TT800 is my primary gigging amp and I couldn't be happier!
If you don't have anything close to you where you can try various amps out, consider an online retailer that has a good return policy like
Sweetwater. Treat the amp like it is borrowed from a close friend and put it through it's paces at home. If it's not for you, contact your sales rep and return it. As long as you aren't abusing it and you are using white gloves (so to speak) they will work with you! It's not going to be the same as gigging with it but neither would trying it out in a shop. You should know enough about it to fall in love or know it's not for you.
Side note...the 803 is a great amp but I'm telling you as a working musician that plays 100 times per year, consider the Subway series and make the investment!