Joined: Mar 2015
Posts: 1,106
Likes: 518
From: New Zealand
Bikes: Gunnar, Concorde, Peugeot 753, Marin, Pete Tansley, Rocky Mtn, Worldrider, Francis Quinlan, Bob Jackson, Winora, Avanti, Klein, Quintana Roo, Shogun, Carlton, Emmelle, Specialized
I'd go for a 13-26 and a triple on an 8 speed bike that sees hills.
If you can keep your shifters, it won't be much more money than replacing your chainrings. A new FD or BB is cheap if you need either. Anything else is just a half measure.
32/42/52 or 30/40/50 for a quick road bike.
24/32/46 or 28/38/48 for maximum comfiness
There's no need to give up close gaps on your cassette. You lose a lot of magic when you put a 11-28 or a 11-32 on a 7 or 8 speed road bike. 11 or 12t sounds pointless for you anyway.
You can get all flavours of 8 speed shimano cassette from wiggle for less than $20. Chain reaction cycles, merlin cycles or amazon are other good places to buy parts/ tools for cheap.
Sugino makes great triples. You have a much bigger range or triples to choose from with an 8 speed bike than with an 10 or 11 speed bike.
You could get a suitable Sugino triple from Riv (or not pay the tithing and get it for less on amazon).