Been reading this  thread a seeing I have a duel core & sli rig I have been  doing a few benchmarks with FRAPS over a set route.
  CPU affinity was set to either 1 or 2 
  SLI was either on or off with all other settings controlled by program.
  Option 5 was using a Nvidia profile copied off trs2004 in control panel
  Trainz options are my own settings except for option 1
These are the results I got
Dave
  -DepthBits=24 
  -StencilBits=8   
  -fullscreen
  -Jet=bin
  -cabinfov=65
  -driverfov=55
  -DefaultAutoMip=none
  -ColorBits=32 
  -frequency=60 
  -width=1024
  -height=768 
  -ResourceMemory=1536
  -LoadingTime=5
  -KeepParticles=1
  -KeepAllResources=1
  -ForceRealtimeLoad=1
  -AreaLimit=14000
  -SectionLimit=50
  -AutopilotSignalDistance=350
  -Intro=disable
  -showkuids
  -FreeIntCam
  -heartbeat=0.01
  ////////////////////////////
  // REQUIRED OPTIONS (DO NOT CHANGE)/ 
  -time=0.0
  -zfar=15140   
   
  PC Specs
  
Box :Antec p180 & true control 500w p/s
  Processor: AMD Athlon 6400 X2 Dual Core  
  
Motherboard: AN9 32X series  3.00 gigahertz
  
Memory: 3GB 800Mzh duel channel 
  Graphics: Xpertvision 7800GT  (2x in SLI mode)
Drivers: Nvidia 6.14.11.6921 
  Storage: 4x Samsung 200GB SATA-II   plus 2 x 200GB external backup
Sound: SB 5.1
  OS: Windows XP-Home SP2
  Optical : LG multidrive DVD burner
  Monitor olyview V372 17 flat panel  8ms response
  Printer/fax : Brother
olyview V372 17 flat panel  8ms response
  Printer/fax : Brother MFC-240C
Anti-virus/spam & Firewall: Zone Alarm
   
   
  1.
  Out of the box settings for Trainz & single graphics & duel cpu
  Min 9         Max  61    Avg 52.628
   
  2.
  Out of the box settings for Trainz & SLI & duel cpu
  Min 7         Max  64    Avg 55.25
   
  3.
  Using Trainz options & SLI & duel cpu
  Min 11         Max  64    Avg 56.969
   
  4
  Using Trainz options & nvidia profile in SLI duel cpu
  Min 9         Max  63    Avg 48.61
   
  5.
  Using Trainz options & single graphics & 1 cpu
  Min 2          Max  51    Avg 24.838
   
  4
  Using Trainz options &  SLI & 1 cpu
  Min 19         Max  64    Avg 58.1777