In AIO lenovo is good c440 is good AIO, If you want gaming then go for lenovo c320 .
again both of this are too costly for what they offer.
Think about assembled one.
in 40k you can built a beast.
Agree with Ankush28..
AIO are not that much powerful.. Go for assembled one which would be way more powerful than any AIO..
If you are okay with assembled one then here a config as per your budget:
INTEL I3 3210 -- 6500
GIGABYTE H61 -D2H -- 3250
CORSAIR 4GB 1600 -- 2100
NZXT GAMMA CABINET -- 2500
DELL IN2030M LED -- 6100
CORSAIR CXV2 430W -- 2650
SAMSUNG DVD RW -- 900
WD CAVIER BLUE 500 GB -- 3100
LOGITECH COMBO -- 700
CREATIVE 2.1 -- 1250
SAPHHIRE HD 7770 1GB -- 8000
TOTAL 37050