traffic
One of the things I haven't seen the Fred/Stafford/Woodbridge/Dale city contingent mention that I95 congestion is -daily- not just weekdays.
Saturday. Southbound after 11 am backed up from Beltway to at least Lorton.
Northbound backed up from PW Pkway to at LEAST 123, usually US 1 and beyond.
Sunday: Southbound after 11:00 to past Lorton.
Northbound: H*ly C*w. Anywhere from Doswell (Kings Dominion) to Massoponax to Stafford, then again from at least Fred through 234.
If you decide on locales south of Fairfax, you're going to be spending a LOT of time staring at someone's bumper.
If you can afford to, get a house that's reasonably close in - as you indicated Springfield, Alexandria in Fairfax county maybe Annandale. You can get 1/2 acre for less than .5 mil right about now because nobody's buying. It is a huge buyer's market.