I'm at pretty much the same point as you. There are plenty of options on the table. Atmel has the SAM stuff, NXP has the LPCs, ST has the STM32.... pick a vendor.

The ARM M-series is a line of devices intended to compete in the microcontroller space. The M0/M0+ is the lowest-end, and each tier builds upon the former. The M4 for example is a pretty capable platform, just shy of a "real processor", and has an M4F variant with floating-point support. You can run uclinux on the bigger ones, with memory in the 100-256KB range or so. Otherwise, you'll be using typical bare-metal code like on AVRs, or an RTOS.
Wikipedia's ARM M article is a good place to get your head around the core options, and the level of control each vendor has on what their flavor will look like compared to the reference design.
Dev boards can easily be had for $20-40 US or so. The bare chips are in the $1 to $20 range. CAN is definitely a popular option -- nearly as ubiquitous as SPI, i2c, etc.