i just bought a amiga 4000!!!

[Oldsmobile_Mike]

Assuming it doesn't have some kind of graphics card already, +1 for the Indivision.  Configuration can be a little tricky, especially with the AGA version, but being able to use almost any modern monitor with your system does have its perks.  

http://amigakit.leamancomputing.com/catalog/product_info.php?products_id=1170

$850 USD isn't a bad price assuming it's in good condition and has at least what I'd consider "a few modest upgrades".  Buster 11, maxed out RAM, '040 board, no battery leakage, etc.

Have fun!  

[Oldsmobile_Mike]

can you explain a bit more about those "issue" please?

Well, for one thing the power supply fan is installed backwards.  

You'll probably want to flip that around to the right way, or replace it outright with a more modern one.  There was a thread on that just a few days ago:

http://www.amiga.org/forums/showthread.php?t=55070

[Oldsmobile_Mike]

thanks
if I understand correctly I cant just use a dp23 to dp9 wire to connect my amiga to a modern lcd monitor?
 
 the Indivision AGA is out of stock I need a other option.

No.  Only if your monitor syncs to 15KHz screenmodes.  Most modern monitors do not.  Certain models of Dell do (2320-something-or-other, search the forums).  Otherwise you will need a scan doubler to promote your Amiga to 31KHz screenmodes.

PS - Indivision says it was expected in-stock last week.  They may have some now, or may be getting them any day.  There are other Amiga hardware vendors too, you know.  

Worst case scenerio, just get yourself a cheap-o A520 adapter to test out and make sure the rest of the system works, while you get your display setup sorted out.  

Also, yes, check your caps, as Tonyvdb said.  

[Oldsmobile_Mike]

You can but only ECS screen modes will work.  like DoubleNTSC/PAL, Multiscan, Productivity but NTSC/PAL will not work.  So early startup, and games will not display.  Some very rare monitors, like the one I mentioned a few posts up, will scan to all 15KHz screen modes!  Try to find one of those.  I think there are some BenQ LCD's that also work, use Google to find out more on this topic.

This is partially incorrect.  If your monitor only syncs to 31KHz screenmodes (i.e., most modern monitors), DoubleNTSC/PAL, Multiscan, and Productivity modes should work.  Or at least are supposed to.    The only problem is you won't be able to see your Workbench to select those modes, since natively it boots up with a 15KHz screenmode.  Also, as TjLazer said, Early Startup and most games, etc., won't work because they use 15KHz screenmodes.

http://amiga.lychesis.net/knowledge/ScreenModes.html