This should have been first but, since you blew that chance and got that dirty old saw first, at least make it next. Dust collection should be your next priority IMHO.
In my opinion, Dust Collection should have been first. That is what I did. I also made a different choice than I would have made if I had more experience at the time. I did a two bagger, one micron, 2 hp, unit. (PennState in case you care). It does the job. However, there is no slack. Only one port at a time open or a considerable drop in air movement is noticed.
I am running all six-inch PVC ducting except some drops are four-inch. There are NO 90 degree turns. The ducts stay clean inside; they are taking everything to the DC.
The DP, planer, both sanders, the 17 inch BS are all clean as a whistle. The Delta 14 inch BS is tremendously better than without the DC; however, it is not perfect. I will say the same for the lathe. I have two of the 2 1/2 inch stay in position, flex hoses at the lathe. When I stop and really position them, they do a good job (not perfect). I sincerely believe both of my "problem" spots would vanish if I had more horsepower.
If I were to do it again:
1 Same as this time. Use 6 in PVC ducts throughout using 4 in drops where necessary.
2 Stay with no 90 degree turns.
3 Go to 4 plus horse power.
4 Use a cyclone.
5 Have the collector, itself, in another room as I have done this time.
6 I have two remotes for the DC. I really like that. I have one marked No, that hooks onto the BS (North end of shop) and one marked So that hooks on the lathe to the South. They both, very easily, lift off of the machine and hook in a belt loop. That way I do not have a 40 foot round trip to get a remote if I am North and the control is South.
7 For short runs I slip on a headset hearing protector. For long runs I use the foam plugs. With safety glasses, dust mask, face shield and hearing protection, the ear plugs are much better. However, it takes longer to put them on and I am a type "A."
WHAT EVER YOU DO, PROTECT YOUR EYES, EARS AND LUNGS. Two people who were very close to me died a really lousy death because they did not protect their lungs. Please don't join them. My hearing has dropped off quite a bit (old age has nothing to do with it). I can still hold conversations without too many, "Huh? or "Please repeat that's." However, I have not gone to a movie for 10 years or more because I cannot understand them (hearing, not stupidity). As for the other item; who wants to be blind.
Sorry for the lecture but don't ruin a bunch of your life through neglect.
Enjoy,
JimB