garmin 265 voice volume

Just replaced a troublesome tomtom with a garmin 265 wt, the only compaint i have is the lack of volume of the voice. i have turned it up to 100% but even at that i cant hear it fully in the cab of my van with the engine above tickover and/or the radio on. i never had such problems with the tomtom.
I know you can download more voices, but is the volume the same on all or is there by any chance a clear female voice with plenty of volume available, i suppose not but want to try.
thanks

can i add that it is the text to speech voice which is weak, the normal english lady is fine but then i dont get the name of the roads