I wanted to come back to this thread to offer a bit more of a real world perspective of what its like owning a car of this nature. I had a Jaguar XJ which was a similar age and i would say less reliable than the e39 and generally more expensive. I had it for 18 months doing around 30k a year. Here is what it cost over that period. It broke down a few times but i kept it on the road without spending a great deal.
Servicing about £220 (changed the oil every 10k or so and did the work myself)
2x tyres £240 (£120 each)
Suspension bushes £180
Welding to 3 sills and boot pan £270
One seized rear caliper replaced £25 (used, fitted myself)
Belt tensioner £70
new belts £25
LPG reducer replaced £80 (fitted myself)
New batter £110
Total, roughly £1220 in maintenance to keep it on the road for 18 months.
When i was finished with the car it had just shy of 170k on the clock. The heater matrix clogged/broke and i had moved closer to work so i no longer needed a work horse. Nobody really wanted a high mileage v8 and it had a dent on the rear quarter from a lorry clipping me so I ended up selling it for £900 to a chap that wanted the LPG kit for his XJS. It depreciated about £1000 but i did give it some abuse.
As has been mentioned perhaps it's worth waiting until after the baby comes, I have a one and two year old and they leech money out of you. Personally I would go for something like a Toyota Soarer or a GS400 rather than a BMW or Audi.
I would also add that I owned Toyota soarer with the 4.0 v8 1uz. I would say it was the best car i have owned. I only sold it because i got bored of the auto box then realized what a horrible mistake i made. They have appreciated a fair bit since i had mine.
The only issue i had was with an alternator but i had a parts only warranty so that was resolved. The air suspension was superb and i had the after market height adjuster. It was comfortable, reliable, great fun to drive and not that bad on fuel. Good ones aren't that easy to come by now and they do look dated but i would highly recommend one.