Your £60 is buying you a faster response; 3ms versus 5ms – only worth having if you play games or use other fast changing screen applications (this is where most of the money is going). Plus more connectivity, the Acer only has VGA input, the HP includes HDMI & DVI-D (which will give better image quality). Even if your PC does not currently have these outputs, almost certainly your next PC will, or you could upgrade your graphics card.
Built in speakers are not worth having, the sound output is invariably tinny due to the power/size of the speakers.
I upgraded my screen from a 17 inch CRT to a 22 inch TFT about 2 years ago (this is my best upgrade). My screen has DVI-D input and cost around £125, you can now buy an equivalent screen for less than £100.