Looking for a flash for a Nikon D3100 DSLR, looking at?

SU-800 and tge SB-400, one is almost double the price but if I could get alot more range for it, I'd be willing to pay for the bang for the buck, if not that much difference I'd go with the SB-400 at 150 bucks and take the extra money and but a nice aet of filters, any suggestions?

Added (1). Yeah sorry, I meant the SB-800, The SU-800 is a UV relote that triggers two side flashes that are bought separately

I assume that is the SB-800?
If you are trying to save some $ and want all of the functions of the bigger better nikon flashes take a look at the Sigma 610DG Super. It's i-ttl, wireless, has the range of the bigger flagship flashes, etc… It's the only one I know of that is fully compatible with it's functions. Otherwise? Yes, I'd jump on the bigger flash. It's got more power, more abilities, better reach, the wireless off camera option is almost necessary…

An SB700 has enough advantage in power and adjustability over the SB400 that it would be worthwhile to get it. The SB900's extra capabilities are important to some, but not to as many.

For flashes, stick with the camera manufacturer's brand. Although aftermarket flashes often claim to be 100% compatible, they often are not.

The SU800 is not a flash, it is a flash controller.

The SB400 is not a very powerful flash, not all that much more powerful than your on-camera flash. The SB400 is more appropriate for a compact camera such as the P7000/P7100.

Since your camera doesn't have a method of controlling a flash off-camera, you will be limited to using the flash on the hot shoe, or if you buy a remote sync cable, you can control a flash wired off-camera.

I would suggest the SB700, as the SB600 and SB800 are no longer made. Your only other choice would be a SB900, but it is kind of expensive.

http://www.althephoto.com

The Nikon SB-400 Speedlight is an intelligent and versatile external flash unit that provides i-TTL flash operation in a super-compact and ultra-lightweight body at an affordable price.

Designed as an entry-level external flash, this flash is ideal for the compact D-40 digital SLR camera, but it is also useful for hobbyists and professionals looking for a handy i-TTL flash unit offering an effortless bounce flash function. When combined with cameras that are compatible with the Nikon Creative Lighting System, the SB-400 is controlled in i-TTL and D40's M (manual) mode.