State of the art in building access control systems?

We have a 65,000sf building here and have all the exterior doors controlled by an older access control system. It is getting pretty old (circa 1999) and requires some hoops to jump through in programming it. The programming / administration software was abandoned by Honeywell at 16-bit so needs a Windows XP virtual machine to run it. We're looking to upgrade, and I'm doing some research and realized someone here might have some tips. Basically we need a system capable of handling 12 proximity card readers and about 300 users. Bonus points if it wires like a "legacy" system with a central panel and RS-485 to door modules - that way we can reuse the existing wiring. I'm looking at a HID V1000 system right now; with the V100 units at each door we wouldn't have to do much with the wiring to get it working. Something more distributed with CAT5 wiring / etc would require all new wiring to the tune of many thousands of dollars. If that gets us that much better of a system that would be fine, of course.

My confusion on the HID V1000 system is the administration end of things. Does HID make any software for administering it or are they strictly the hardware vendor? It looks like it uses the "OPIN API" and they don't provide the software itself. Is there anywhere to get software that I can set up myself? Is there any way to get the API as an end user?

Is there a better system out there for our relatively simple needs? I am not interested in spending $50,000 on a custom install. That's what we spent on our current system and I ended up having to go take the manufacturer's training and re-do much of the system so it would work right. It was a mess. I would prefer something that I can handle installation and administration of, with "advanced" experience in computers, networking, and access control installs but limited exposure to systems beyond ours. (Northern N750)

Budget is flexible. Obviously cheapest is best but $10,000+ is not out of the question. We would reuse the existing electric door strikes, and hope to reuse the existing wiring, as mentioned.

http://www.aus.com/offices

I deal with these guys in Charleston SC at several of the facilities we service. They seem to be decent. No clue about pricing but they should be able to do anything you need. 

DMP makes a fantastic access control and alarm system. If you can find a local dealer, you could do it yourself if they'd sell you the stuff. 

I don't remember specific models it's been a few years since I installed them, but we had to do rfid cards with varying clearance for a multi use office building. It was way easier than the intercom system we'd replaced. I had to set and test all 300 cards at all the access points, while time consuming, dead simple. 

I also installed DMP fire and security panels, and they're light years a ahead of silent knight and Honeywell as far a programming and technician interface there as well. 

My former employer used Kantech products and we were pretty happy with it.

Do you have a Building Control System (BCS) like Honeywell or Johnson Controls, because almost everyone of those has a Access module available?

We replaced our entire network, rewired all of our schools, and installed a VOIP phone system - all Cisco - before I retired.  Went on a tour at their San Jose HQ and some of the stuff they were doing with building access control was incredible.  Unfortunately,  the money to address our access buildings was simply not there.