Which mountain bike should i buy?

Anyone got any experience with mountain bikes?
Im wanting a new bike cause my old one is stuffed.
they want nearly $500 to get it up to standard (needs new derailers, cogs, wheel etc)
I was going to just go buy the avanti atomic which has gotten some good reviews and only costs $629
http://www.avantibikes.com/comp-mtb/montari.aspx?bid=38
but then i saw one of these GT Avalanche 2.0 and they look really cool.
I can pick one up for about $800
http://www.gtbicycles.com/int/default.a ... ory&&id=17 (you may need to scroll down a bit to find the avalanche)
Do you reckon its worth spending the extra $170 for the GT?
Ive had the last bike for nearly 8 years so i will get the use out of it no worries. but if im not going to notice the difference between them i might as well save my cash right?
got any advice or reccomendations for me?
BTW i need to buy it before saturday as i am going in the sydney to wollongong ride on sunday.
Thanks for the help
Im wanting a new bike cause my old one is stuffed.
they want nearly $500 to get it up to standard (needs new derailers, cogs, wheel etc)
I was going to just go buy the avanti atomic which has gotten some good reviews and only costs $629
http://www.avantibikes.com/comp-mtb/montari.aspx?bid=38
but then i saw one of these GT Avalanche 2.0 and they look really cool.
I can pick one up for about $800
http://www.gtbicycles.com/int/default.a ... ory&&id=17 (you may need to scroll down a bit to find the avalanche)
Do you reckon its worth spending the extra $170 for the GT?
Ive had the last bike for nearly 8 years so i will get the use out of it no worries. but if im not going to notice the difference between them i might as well save my cash right?
got any advice or reccomendations for me?
BTW i need to buy it before saturday as i am going in the sydney to wollongong ride on sunday.
Thanks for the help