You guys know phones, and you know deals! so…
Love my HTC One M7, but the battery is a joke now. Dead by lunch. Got a new job and fancied a treat - the m8 is a bit rich for me still, wondering what everyone thought on phones around $400? Ideally will be an improvement on my M7, but I love it!
Cheers
LG G2. It's <$400 and will woop the M7 in terms of perf. and battery life.
Battery is not replaceable though (technically it IS replaceable but the difficulty level is slightly advanced)
A little beyond your budget is the OnePLus One which rang from $419 for the 16GB ver or $485 for the 64GB ver.
Ideally you will want a phone that has user replaceable battery so you can continue using the phone for a little more than 2 years and not be hampered by the ever-decreasing battery efficiency.. That's where Samsung Galaxy s4 or Note II comes in.
You could also give your old phone a new lease on life by replacing the lithium cell but good luck taking the phone apart. Difficulty level — Insane.