I started with a ace 150, 250 and then went to a at pro and bought nel coils for it attack and tornado. I have seen videos with after markets coils (big coils) on the ace series and it didn't seem to do a whole lot. I started to buy a different coil for ace 250 when I had it and a dealer talked me out of it.. I bought a at pro and it was a big improvement over the ace series. This is the point I'm trying to get at instead of sinking hundreds of dollars in accessory coils wouldn't it be better just to upgrade to the at series or something. I mean your only gonna get so much out of a ace and apparently your already wanting more. The pro zero audio is way better than the ace bell tone, don't know what audio the 400 has havent checked it out. I been thru all that after market coil upgrade business and spent a lot of money doing so and then finally upgraded anyway... could have saved myself some money and trouble. 5x8 isn't going to get you more depth . hope this helps. at pros are going cheap since the new release is coming out. Ive seen them used for 350 or so. What does a coil cost 125.00 ??