There are a few boats on your list that are well proven offshore cruisers but almost all will need some improvement to be considered "bluewater"
I picked Alberg 30, Mainly because it is the boat I have chosen as well.
Many Albergs have proven offshore capable, with appropriate upgrades and modifications.
Alberg 30- check out sailingsalsa.com, I believe in his blog he says all said and done he spent 40K, getting his Alberg ready for a circumnavigation
Also, Pearson Trition, Albin Vega 27, Bristol 27 and list goes on..... are all good boats that can be had for 10k or less with proven offshore capability but prolly not ready for offshore duty until checked, upgraded and refitted.
I bought my A30 for $4800, have put another $3000 in standing and running rigging mods. About to put boat on side of house for a 2yr refit when I plan to completely refit all aspects of boat, this will include many upgrades...tankage being one. So far I have probably $8000 and a very nice base for building an offshore cruising boat for 2. I figure to have about another 5-7k when done. I could probably buy a bigger boat for 20k but it wont be done the way I want with the parts I want in the boat I want so I have chosen to buy a boat at a reasonable cost and upgrade as I go.
These sites below have lots of great information;
Atom Voyages - Home
Voyaging Under Sail, Cruising Lealea Home
Alberg 30 sailboat project
One last note, check out
this guy goes all over the north atlantic(80N) in a 21ft junk rig boat. On his site he detailed about the modifications to make his boat bluewater capable. He has recently upgraded to a 24ft boat(big).... search youtube for "mingming" for video of 21ft boat at sea and the building of MingMing 2(24ft). Very robust and simple.
For me this trick is going to keep all systems as simple and basic as possible.
Good Luck in your search