Hmmmm, that is odd. Yes, even my GTX 480 offers 1600x1200:
root@imerabox:/# lspci | grep VGA
05:00.0 VGA compatible controller: NVIDIA Corporation GF100 [GeForce GTX 480] (rev a3)
root@imerabox:/# hwinfo --framebuffer
02: None 00.0: 11001 VESA Framebuffer
[Created at bios.459]
Unique ID: rdCR.5E8TF6cNmo5
Hardware Class: framebuffer
Model: "NVIDIA GF100 Board - 10220000"
Vendor: "NVIDIA Corporation"
Device: "GF100 Board - 10220000"
SubVendor: "NVIDIA"
SubDevice:
Revision: "Chip Rev"
Memory Size: 14 MB
Memory Range: 0xd5000000-0xd5dfffff (rw)
Mode 0x0300: 640x400 (+640), 8 bits
Mode 0x0301: 640x480 (+640), 8 bits
Mode 0x0303: 800x600 (+800), 8 bits
Mode 0x0305: 1024x768 (+1024), 8 bits
Mode 0x0307: 1280x1024 (+1280), 8 bits
Mode 0x030e: 320x200 (+640), 16 bits
Mode 0x030f: 320x200 (+1280), 24 bits
Mode 0x0311: 640x480 (+1280), 16 bits
Mode 0x0312: 640x480 (+2560), 24 bits
Mode 0x0314: 800x600 (+1600), 16 bits
Mode 0x0315: 800x600 (+3200), 24 bits
Mode 0x0317: 1024x768 (+2048), 16 bits
Mode 0x0318: 1024x768 (+4096), 24 bits
Mode 0x031a: 1280x1024 (+2560), 16 bits
Mode 0x031b: 1280x1024 (+5120), 24 bits
Mode 0x0330: 320x200 (+320), 8 bits
Mode 0x0331: 320x400 (+320), 8 bits
Mode 0x0332: 320x400 (+640), 16 bits
Mode 0x0333: 320x400 (+1280), 24 bits
Mode 0x0334: 320x240 (+320), 8 bits
Mode 0x0335: 320x240 (+640), 16 bits
Mode 0x0336: 320x240 (+1280), 24 bits
Mode 0x033d: 640x400 (+1280), 16 bits
Mode 0x033e: 640x400 (+2560), 24 bits
Mode 0x0345: 1600x1200 (+1600), 8 bits
Mode 0x0346: 1600x1200 (+3200), 16 bits
Mode 0x034a: 1600x1200 (+6400), 24 bits
Config Status: cfg=new, avail=yes, need=no, active=unknown
root@imerabox:/#
Yes I would expect the blob to outperform nouveau. I had to go the other way -- on a Dell E6500 nouveau gave me a 1600x1200 tty console, and my old eyes had problems seeing the tiny font, although the desktop was beautiful. I finally installed the blob so I could get a 1280x1024 console that I could read.