The internal tuner in the 480 has loss insertion, like any tuner would, so 
the 10 watt loss is unavoidable.
The STG tuner will tune the antenna, but you shouldn't use the internal 
tuner at the same time.  That will get your 10 watts back.
The CW filter really livens up the ts-480.  As far as the pre-amp, depends 
on your location background noise, and signal strength.
I use it here on 24 MHZ and up.  I also back the RF gain back to 88 in the 
menus, to try to help with the signal to noise ratio.
Unfortunately my other receiver is a Tenteck Omni D, and their is no way 
that a ts-480 will be anyway near as quiet as that analog radio.
Also, you will have to adjust the CW weight menu option, from the default if 
you send at over 27 WPM.  Your fist will send krap if you don't adjust that.