I have done all of the above installing the alternative version and altering the settings to direct sound. All of this has improved the general copious amounts of micro stutters but didn't stop all of the odd split second dropouts of audio. Now my collection is getting on for 30,000 tracks and all albums have album art and I found just scrolling down the Album lists could trigger a split second jump, also using the internet.
SO I thought I would try turning off my wifi on my laptop whilst the music was playing and observing the task manager performance of ITunes and immediately saw a 2 or 3% increase of use on the cpu and experienced a long dropout on the audio. This happened every time I repeated this.
To continue (sorry for long explanation) I decided to sign iTunes out of my Apple ID therefore not being connected to iTunes Store (though you can still access it) within iTunes and as if by magic no more audio dropouts so far regardless of wifi on/off or internet usage???? So my guess is there is an issue within the true 64bit design of iTunes 12 to work with windows 8.1 regarding its internet connection.
If anyone else out there is having this continuing issue regardless of trying all the previous suggestions please try signing out of your Apple ID account and see if this helps alongside all other options.
After much more use and testing turning the wifi on and off can still on occasion trip the audio dropout but in general I am having far less issues with dropouts purely by not being signed into my Apple ID when signed in I am having frequent dropouts every track or so with light laptop use with this latest (alternative) iTunes update 12.1