Hi Rog,
I've got 3 yds of track, a Lenz DCC unit, and very quickly decided that that was enough to warrant soundchips in all my engines. I then discovered the Huddersfield Railway Modellers, and between three of us we re-wired the entire O Gauge layout to take either DC or DCC feeds which opened up longer running (and some new sounds when the engines were up to speed too!).
If you've an inclination towards sound, andalso have invested in a DCC controller, then I'd choose to have fun with the fine control and sound on even the shortest lengths of track - andI really do advise you to go and join a local club - most are really welcoming of new blood and it can great fun too. Most have moved to some DCC layouts and getting that throaty roar of a Maybach leaving the station gets me every time! (But then I am biased
).
Hope you come down on the side of the soundcard.
Cheers for now,
Ian.