Mac Book Pro 15" RAM upgrade

curiousity

slm,
aku bercadang nk beli Mac book pro utk wat keje2 grafik cam 2d & 3d design(Revit,sketchup,lumion), photography, video,etc...
mula2 tu cdg nk amik MBP 13" 2.8 ghz tu tp takut tak laju utk wat rendering...pastu skang terfikir nk amik MBP 15" 2.2 ghz plak...soalan aku berbunyi :
1)utk keje2 grafik yg aku sebutkan kt ats, agak2 memadai tak kalo angkt 13" je,tak perlu la smpai 15"(tp yg ni best sb quad core+amd Hd)?
2)kalo yg 15" 4gb RAM tu,ada sape2 pernah upgrade jd 8gb tak? kalo kita upgrade sendiri RAM (cr yg compatible) agk2 ada effect yg tak best tak? (cam void warranty sb pndai2 godek sendiri,performance laptop tiba2 jd down?
3)recommended shop selain kt machines tu...& ada dpt freebies tak kalo beli kt kedai2 komputer@authorized dealer ?
sekian,tq
skang tgh excited nk beli sebiji epal ni..

budingyun

kat apple store boleh terus configure + lagi 4GB (RM680) http://goo.gl/A1MI0