Well, Wardensville is a mere 2hours or so from the Manassas area and is right next to the National Forest. IIRC, a friend of mine bought a piece of land (5ish acres) with house, pool, dsl service available, etc for less than $300k. It backs up to the Nat Forest on the WV side. His commute sucks at 2hrs, but it's mostly highway and he does get to live in the country.
I think I pointed this out in another thread, but I saw a 100acre parcel of land off of Rt55 between I81 and Wardensville (Va side of mtn) go for about 90k 6-7 years ago. That was only an hour or so from Manassas, but well out of NoVa.
Depending on where you live, 4hrs puts you solidly in SW Va (Roanoke area), where you could probably find what you want much cheaper. Also check out the area around Harrisonburg. It's a college town and land might be more there than it otherwise would be, but it should still be cheaper than anything close to NoVa. That's about 2hrs from NoVa. Going south, you probably won't get significantly cheaper until you get past Richmond (2+hrs). That includes Nokesville, Catlet, etc. Anything within 2hrs of NoVa is subject to price inflation due to commuters, especially if there's train service. Properties two hours west via I66 are somewhat protected by the horrible traffic on I66 itself. From Mclean (where I work) to Manassas is an hour most days. I81, a mere 45 miles further west, is another hour during rush hour. There's no commuter train service in that direction that I'm aware of. Therefore, property two hours west via 66 is frequently cheaper than similar properties two hours south via 95 (Folks that far will take the train to DC).
Anyway, my point is to look into Southwestern Va (including Shenandoah Valley) or West Va (away from bedroom communities). Four hours' drive gives you a lot of flexibility. However, add an hour to that if you plan to make the trip during rush hour on Fridays.
Chris