I have no idea

Hello, I'm thinking of brushless and was looking at the HV-Maxx set-up for my basically stock E-Maxx. However, I'm also considering lipos, which lowers my voltage to 7.4v per pack rather than 8.4v per pack. I still want to top 40mph comfortably (as I have a friend with a Revo 2.5 who I HAVE to beat!) and be able to bash with a good run time. I don't race.

So, what's a motor/ESC combo I should be looking at without going too wild? I reckon on spending not too much more than the HV-Maxx, so would I be OK getting that, or can I spend a little more and get more wallop? And I also would like good low-speed control for just pottering around the back garden sometimes.

Thanks in advance for your input!