Alright, I have been trying to get FTB Unleashed to run in a somewhat playable manner with the settings recommended in this thread, I use the standard FTB launcher and just followed the instructions to paste the commands and set allocated mem to 2Gb. First thing that happens when I do that: 
http://pastebin.com/GXdbNkeY It simply runs out of memory, I allocate any more then 2Gb (aka 4Gb and up), it starts off fine but as the world loads it starts to stutter up to a point where it becomes unplayable, adding on to that, it decides to eat trough 10+Gigs of RAM. For reference, here's a pastebin from when I used 4Gb RAM with the same JVM commands: 
http://pastebin.com/CywpdStW
I also tried running Unleashed with the MultiMC Manager, followed all the steps but the same things happen.
My specs:
Operating System
    MS Windows 7 Home Premium 64-bit SP1
CPU
    Intel Core i7 2600K @ 3.40GHz
    Sandy Bridge 32nm Technology
RAM
    16.0 GB Dual-Channel DDR3 @ 802MHz (10-10-10-27)
Motherboard
    ASUSTeK COMPUTER INC. P8Z77-V DELUXE (LGA1155)
Graphics
    ASUS PA238 (1920x1080@60Hz)
    1279MB GeForce GTX 570 (ASUStek Computer Inc)
Hard Drives
    119GB M4-CT128M4SSD2 (SSD)
    932GB Western Digital WDC WD10EALX-009BA0 (SATA)
    932GB Western Digital WDC WD10EZEX-00ER1A0 (SATA)
    466GB Seagate ST9500325AS (SATA)
    466GB Seagate ST950032 5AS SCSI Disk Device (SATA)
Edit: Forgot to mention that I downgraded my Java 7 form u45 to u25 because I read this in another post from Eyamaz about stutter removal, fyi things were just as bad before the downgrade.