HELP with purchase: 2009 SSD vs 2011 Base

I currently have a 11" MB Air and I love its portability but I don't like the small screen. I am currently working at home so the MB Air isn't very practical in terms of screen size. I want a Mac Mini so I can just hook it up to a tv/monitor or anything bigger than 11" and do more with the screen when i'm at home. Anyway, my primary uses are word doc, videos, internet (basically, all school & media entertainment purposes). Also, HD space doesn't matter to me as I store everything on an external hd that I already have.

Should I purchase:

a) USED 2009 Mac Mini - 2.26 Core2Duo + 120GB OWC SSD + 4GB RAM for $490?
-i love the SSD & the upgraded RAM (as it'll basically mirror my MB Air)
-I like having the option of a cd drive or removing it for a 2nd hard drive
-i love the price
-i have a mini-dislayport to hdmi adapter already
-although an older model, i like how i can still install the latest OSX - Lion

or

b) REFURBISHED 2011 Mac Mini Base - 2.3 Core i5 + 500GB + 2GB RAM for $550?
-i love having the core i5 processor
-i like how there's no power brick
-i like how there's a sd card slot
-i like how there's a separate HDMI port

or

c) USED 2010 Mac Mini - 2.66 Core2Duo + 320GB + 8GB RAM for $490

or

d) USED 2006 Mac Mini - 1.83 CoreDuo + 80GB + 2GB RAM for $250
-i love how it's really cheap
-i don't like how it can't be upgraded to lion but then again, I've read that some people prefer Snow Leopard over Lion.
-but will this be fine for what i do without getting me frustrated with the lack of speed?

or

e) none of these are worth the price

couple questions:
-which configuration will be fastest? How would you rank the order?
-would i be able to install Mountain Lion in the '09 model when it's released?

THANK YOU!