Upgrade M6400 or move to M4600?

I have a 2 year old M6400 with the following specs:

17" 1920x1200 RGBLED anti-glare, Quadro 3700M, QX9300 2.53Ghz quad, 8GB RAM, 2x Dell/Samsung 256GB SSD in RAID 0


Here's what I don't like about my current setup:

Because I am running the SSDs in RAID 0, TRIM doesn't work and the drives are pretty degraded performance-wise. What was fast 2 years ago isn't by today's current generation SSDs.

The power brick (even the smaller "slim" model) is massive and poorly suited for travel. I use the standard one at my office and the slim one at home so I don't have to carry a charger with me.

Battery life is horrible. I can only get an hour at best on the M6400, worse if I am working in Lightroom or Photoshop. The video card is running all the time no matter what (no Optimus).

Pretty loud with the fans running and still hot.

Not 6GBs SATA. ​

Here's what I like:

I do love the RGBLED 1920x1200 screen. I do a lot of photo editing and managed to calibrate mine perfectly to get rid of the blue tint. Really one of the nicest laptops screens around, with plenty of real estate.

Still pretty quick with the quad core 2.53Ghz. ​

What I like about the M4600:

Better battery life. Some around here are reporting as high as 8-9 hrs with casual use and 2-4 hrs with some serious procesing (LR, PS). That means that the computer becomes useful for travel.

2lbs lighter weight.

Sandy Bridge, quad core hyperthreaded i7, USB 3.0, HDMI, 6GBs SATA

10-bit IPS display. Although it is only 1920x1080 and you lose Optimus switching which tosses some of the batter life out the window.

Touchscreen, although appears to only be an option on 1376x768 low-res screen, not on the IPS LCD. Bummer, really.

Smaller power brick, smaller laptop footprint and still has number pad.
​

So, here's the dilemma. I could upgrade my current system or I could go with the new M4600. I would do the following upgrades to my system:

Change out the 2x Samsung SSDs in RAID 0 with a single 512GB Crucial m4 ($775) and a WD 750GB 7200RPM Scorpion ($100). This would give me much faster single drive with TRIM and even more near-line storage with the WD HDD. I wouldn't get 6GBs speed from the SSD obviously, but the all-important 4KB random-write shouldn't be effected.

Upgrade from 8GB to 16GB of RAM for $100. Can't ever have enough RAM.

Get USB 3.0 EC54 card ($12)​

So, for about $1000 I should have a much better performing system with more than double the storage space and RAM, along with screen I already know I like and have tweaked to perfection.

I would reasonably expect to spend exactly the same upgrades to a new M4600 (along with optical bay caddy for HDD), bringing my estimated total to $3400.


A few questions:

1) How much faster is the i7-2820QM than the C2D QX9300 in applications like Lightroom and CS5? I don't care about games at all.

2) Along the same lines as the first question, how much performance improvement will there be with the Quadro 2000M vs. the Quadro 3700M? Adobe programs use CUDA acceleration.

3) How much better is the 10-bit IPS screen than the RGBLED LCD and is it worth losing some screen real estate?

4) Will I still get better battery life using the IPS screen if Optimus is disabled and the GPU is running 100% of the time like I have now?​

I'd appreciate any feedback or advice from people that have had both. I'd also welcome input on the M6600, although I'm not sure what I would gain over the M4600.

Thanks!