Riley is where Vic was... Here are my thoughts on the stuff you mentioned:
The Avionics guy quoted me $16000 from the hip for a 430W and KT-74. I think that is a bit high. I see 430Ws showing up for around $7k from people upgrading to GTNs. With the KT-74 street prices around $2,600, I agree $14k is much closer to the right installed price. I agree with the others. The 430s are nice, but the GTN 650 is what you want.
I can go with a GNC255A and the Stratus ESG later. The 255A would be about $6000 installed and the ESG about $4200. My plane was VOR only until I upgraded to the GTN. I would not go non-GPS knowing what I know now.
Since I would be taking a loan for all this, what should I reasonably expect on cost for an Aspen Pro retrofit? I am non-autopilot, so I was thinking around $13000. Would safe to assume? I think if you shop around you may be able to get one installed for $11k - $12k. If Riley is tight for panel space, the Aspen will free up the VSI spot for you.
If you want to compare notes on upgrade costs, let me know. I did my upgrades in the Fall of 2012, but it should help show reasonable install costs. I did get a number of different quotes from shops around me.
I know our planes are pretty close to the same age. As you probably know, I did the big jump with the avionics. Never regretted the decision. My situation was a bit different. I have owned my F since 1991 and have been steadily saving for an avionics reserve for years. So, other than a shaky hand as I was writing the check for the avionics bill, I have been enjoying the heck out of the avionics and the fact Vic is much more capable.