but what kind of lumens is considered normal for an MTB light these days
Crickey. Thats a difficult one. Bit like that thread recently "how much light is enough" or something like that.
The Model 601 has an on-paper maximum of over 2000 lumens, paper lumens as I refer to them.
Last year I actually went for a lux reading, independantly measured in a lab. Result of 70 Lux at 10 metres.
But as you probably know, theres a light out there for eveyone, from a couple of hundred Lumens to a couple of Thousand.
So then I suppose it comes down to other factors and what you feel you require, such as build quality, runtime, durability, easy of use, etc, etc.
imo