Can't tell you about solaris, but it boot in about 20s (if no additional apps installed), default configuration in a P3 1Ghz running Windows 2K with 512Mb.
In another machine, P3 800Mhz running suse 8.1 with 128Mb RAM, it boots in 1.5 minutes, but has an issue tracking application installed, and the machine is heavilly loaded.
So I think something is wrong on your side. Did you change any logging configuration ?
If you intend on running Solaris and expect performance thenn either get a machine with an ultra 3 CPU in it or run it on an intel box with a Xeon CPU.
You will need at least 512M of RAM, I would recommend at least 1G but it all depends on what your applications are like.