If your actual machine is a Dell as listed in your stuff, the following is not an issue. But you may wish to get a copy of parallels virtual, so that you can run all your current pc software in whatever you are currently doing. This would make your transition to a mac very easier. I have some software that will NEVER be put into apple format, and I run it in unity with my mac. I click on the item and it simply opens even though its running in windows xp, I don't know that. It seems like its running on my mac.
If you ahve a mac now, our biggest problem here is that you may have a lot of legacy software that won't run on Lion. You need to address that issue before you buy a new machine, migrate your stuff, only to find that 3/4 of the software you use everyday no longer works.
P.s. : I understand the fixed income, I get my "entitlement check" on the 4th wednesday of every month.