Here's what I was able to find out about your motherboard.  It's a socket AM2+ motherboard and is apparently backwards compatible to AM2 processors.  So the Athlon 64 X2 6000+ might work.  The TDP (thermal design power)  is the only concern I have.  It's a 125W processor and the motherboard might not be designed to handle that.  As an alternative, you can upgrade to a Phenom X3, Phenom X4 or the newer Athlon X2, such as the Athlon X2 7550.  These are all AM2+ processors.

The AMD website tells me that the 6000 is 89W, what is the most amount of watts that I should put onto my motherboard?

The one you list however is 125W version.  There is actually three versions of the 6000+:

• ADX6000IAA6CZ - 125W Athlon 64 X2 6000+ 3.0Ghz Windsor.
• ADA6000IAA6CZ - 89W Athlon 64 X2 6000+ 3.0Ghz Windsor
• ADV6000IAA5DO - 89W Athlon 64 X2 6000+ 3.1Ghz Brisbane

Do you know what the highest watt CPU is that I can put on my motherboard?

It will take at least a AMD Phenom II X4 945 Processor (3.0GHz) processor, because Dell is currently offering  a 546 in the Outlet with this CPU.  It's advisable to always have the latest BIOS update before upgrading the processor.

would the AMD Phenom II X4 945 Processor (3.0GHz)  95 watt work in the Inspiron 546 motherboard ?

If you read the previous post you would have your answer.

errr Now ! Was just worried bout the thermal ! Wattage !

Cool ! How i'll order it ! Thanks

If Dell sells this model with that particular CPU then you should be fine.