One of the most affordable places I've found spirals (and fast shipping) is
Quality Wine and beer Supply.
I also break my spirals, depending on the wine I am making, my Melomel usually only get 1/2 depending on the type of wine, and the toast level.
I've layered oak using them as well, the beauty of it is that they do not impart a ton of oak at once like chips, so I can get the the flavors that i want out of them without having to worry about it happening very fast and over oaking.
I like a nice Medium Plus toast on some of the big Italian Reds, I've had Medium chips impart a strong vanilla in one batch....not exactly what I was going for..
Here is a list of what the various toast levels will bring to your wines, borrowed from the barrel Mill website:
Heavy Toast brings pronounced caramelized, carbonized and toast flavors very quickly.
Medium Plus Toast Is between Medium and Heavy Toast. It has aromas of honey, roasted nuts and a hint of coffee and spices.
Medium Toast has less tannins but more bouquet, so will impart more aroma than flavor. It has a warm, sweet character with strong vanilla overtones.
Light Toast fresh oak, coconut and fruit flavors.