first and most important, don't get a bead filter with the air pump for back wash like those advantage bead filters. get an Ultima II bead filter. Ultima that Don mentioned is the one to go with. with your pond size, you can do one Ultima I I 6000 for both bottom drain and skimmer. Follow by biofilter with Matala up flow or J-mats. I recomend the biofilter size equivalent to at least 15% of your pond water. that's 375 gals biofilter for 2500 gals pond. my friends use Artisian pumps are whisper quiet. it's amazing. Artisian pump is my next replacement pump.
Using Utima as mechanical after settling tank is a good approach. it helps with weekly maintenance. here is what I do. I do partial flush settling tank each morning to get the overnight fish poops out and another partial flush when I get home from work. I build it so that I can do partial flushes with gravity force. it takes a few seconds for each partial flush by opening the knife gate valve. I empty the settling tank once a week on weekends and backwash the Ultima once a week but it's either on tuesday or Weds.
I don't use UV light in my pond ever even when it was brand new. the water is clear enough to see the bottom so why bother with UV light. My pond gets about 90% of full sun from morning until sunset. I feed my fish a lot and I meant a lot.
Steve