I have 2i2 focusrite Scarlett.Looking for an upgrade...more I/O and better preamps , dual headphones.Scarlett itself has higher models.I hear a lot about RME and Motu.Do the RME and Motu sound better than Focusrite? They are much more expensive than the Scarlett models.Wondering if its worth the price.

I haven't used or even heard a Focusrite or MOTU interface, but I own an RME Babyface, and I can say that it sounds absolutely excellent, and has -- by far -- the most stable and efficient drivers of any piece of hardware I've ever used.
 
Good drivers are worth a lot. No point having sweet sounding hardware if the drivers are not up to the task. RME offers the best of both, IMHO. I cannot recommend them enough, and you certainly get what you pay for...
 
 
 
 

I used to have a Focusrite Saffire Pro 40, I've had others and now have an MOTU 896mk3 Hybrid.  The Saffire Pro 40's preamps, compared to Roland Octa-Capture (that I used to have) and now the MOTU tended to not to produce sound as full fidelity (guitar, for example, sounded like High/Presence controls on an amp were cut) as the Roland or MOTU units.  I always liked the Saffire Pro 40 preamps until I had to replace it and heard the preamps in other units.  The MOTU preamps are even better, I used to use an outboard preamp for vocals on the Roland Octa-Capture, but I find I don't need that with the MOTU.
 
I had considered a new Focusrite Scarlett but was told the preamps were the same as used in the Saffire Pro 40, so that was removed from my "short list" when I bought a new unit.   
 
My 2 cents. 
 

I upgraded from a Focusrite Pro 24 to a Motu 828MK3 Hybrid. The difference to me is night and day.  The pre's are very nice, better than I expected. If I could afford it I would have bought an RME Fireface UFX. You can't go wrong with the Motu or an RME.

I'm not happy with my Scarlett's pre amps so I don't use them. You can always buy a better pre amp so I use a Joe Meek 3Q.  For my next interface might be the Tascam UH 7000 just to get the pre amps , If I had the money I would certainly look at RME..  
 
As I always say, make a wish list of what you need first before shopping.
And putting solid drivers at the top of the list is always a good choice.

Conventional wisdom (around here) says RME would be at the top of that list.
 
The only way I would replace my RME UFX is if it simply died (into an unrepairable state) and I'd replace it with a new RME UFX.

Well, as a general principle, out of those manufacturers I'd put RME as the top one, then Motu and Focusrite last. However, the law of diminishing returns kicks in as it does with all things. An RME that costs twice as much as a Focusrite won't have "twice the quality". What it will have is a higher build quality, which shows up as a reduced noise floor and what are amongst the best, maybe the best, external interface low-latency drivers in the business. And a superb software control application/digital mixer and a fat manual.
 
My Focusrite Octopre is slightly noisier than the UFX if I use the October mic preamps, but I mostly use them as line inputs where they're OK. The mic pres aren't so noisy as to be a problem, but the RME ones are a bit quieter and I think a bit flatter in their frequency response. At least, that's what running white noise through them and taking a look at the resulting spectrum says. Not a huge difference though. As I said, there comes a point where spending more and more gets you less and less in the way of obvious improvement.
 
RME also have a history of supporting older products well. Since they recently replaced the UFX with the UFX+, the biggest change being replacing the Firewire socket with a Thunderbolt one, they'd better keep on supporting old products or I'll be quite annoyed with them.

The safest bet is certainly RME, considering its long term support for devices and its track record for driver stability.
 
I recently got into the MOTU AVB interfaces as I needed more I/O than I could get with one interface and the new AVB features are outstanding as regards scalability, clocking, routing. Latency is top of the pops. Don't know how many I/O channels you need, but if you feel you might be expanding later on the UltraLite AVB might be an interesting option.

Here is a more precise description of what I do with the audio interface :
 1) I work mostly on video projects. I record 50% of the time in-the-box. The other 50% is vocal and instrument tracking, mostly 1 or 2 at a time. I don't record a full band at the same time.
 2) I need to monitor my mixes on different studio monitors, so I need multiple outs (atleast 4, planning 6 for a third pair of monitors in the future )
 3) I need 2 headphone outs preferably .
4.) I am on Windows (obviously being a long time sonar user) and have a firewire PCI card on my motherboard.
 
While I was looking for a monitor controller for (2) and (3) I figured out an audio interface upgrade might as well cater to my monitoring needs plus if I can get better sound and performance than the focusrite, then I rather go for a AI than for a monitor controller.
I am also wondering if its worth getting a firewire interface when most new interfaces are either Thunderbolt or USB .
 

RME is like a Sherman tank - it's not gonna stop unless you blow it up :O) I have two (UFX and an old HDSP9652 Card - since 2003). Both just work, all day, every day. And both get regular driver updates (even the 2003 model)
 
The RME pres are very clean and forgiving. Not "warm" but very pure IMO.