If you get a transfer to the Southern League you'd join the Central Divn not the South & West, so Hereford, Salisbury, Taunton etc. gates are not really relevant.
The Central Div. would give you a good number of local derbies plus Aylesbury and Aylesbury Utd (playing at Chesham next season), making travel to the away games easier and boosting the gates.
In my opinion that would be much better for Harrow Borough than the Isthmian Div 1 North.
I am still hoping Borough may get a reprieve, having the best points per game ratio of the relegated clubs. That could happen if there is an enforced relegation or denied promotion incident elsewhere.
The future ? I suspect that the height of ambition for Clubs like Harrow would be National Conference South plus the odd good cup run.