Ok, for those curious, here is a comparison between the SB6120 and the SB6180. 
Bottom Line:
Overall performance is dead even, but with the SB6180 having 8 channels, that performance will no doubt stay more consistent through peak times during the day. Also, the SB6180 gives you much more info on your signal. I especially like the ability to see your configuration file (Speed tier and IP). The one down side is there seems to be a bit of a delay switching between options on the modems diagnostics, but I think thats because its pulling more data for the interface. Considering a SB6120 cost 79-99$, and I bought the SB6180 for 69$, I would say its a very good deal. I will save my final recommendation after using it for a week or so, but so far so good.
SB6120Status   Signal   Addresses   Configuration   Logs   Open Source   Help
Model Name: SB6120
Vendor Name: Motorola
Firmware Name: SB612X-1.0.5.1-SCM00-NOSH
SIGNALChannel ID   2    3    4    11 
Frequency   843000000 Hz    849000000 Hz    855000000 Hz    879000000 Hz 
Signal to Noise Ratio   37 dB    36 dB    36 dB    37 dB 
Downstream Modulation   QAM256    QAM256    QAM256    QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
0 dBmV     -1 dBmV     -1 dBmV     0 dBmV  
Upstream   Bonding Channel Value
Channel ID   1 
Frequency   25600000 Hz 
Ranging Service ID   3375 
Symbol Rate   5.120 Msym/sec 
Power Level   44 dBmV 
Upstream Modulation   [4] QPSK
[2] 16QAM
Ranging Status   Success 
PERFORMANCEhttp://www.speedtest.net/result/1595625740.pngBoston 32.21 7.32 17ms
http://www.speedtest.net/result/1595633068.pngNY 32.35 7.19 11ms
Pingtest.net
Philidaphia 22ms 1 ms A
http://myspeed.visualware.com
Test Type:   Application Speed
Location:   
Download Speed:   32741 kbps
Upload Speed:   6871 kbps
Speed Consistency:   99 %
Round Trip Time:   16 ms
Max Delay:   36 ms
Average Delay:   1 ms
Bandwidth:   33600 kbps
Max Route Speed:   32767 kbps
Forced Idle:   6 %
Route Concurrency:   1
Test Type:   s / s
Round Trip Time Consistency:   100 %
SB6180Software Version: SB6180-3.2.1.0-GA-00-252-NOSH 
Hardware Version: 1 
MIB Version: II 
GUI Version: 1.0 
SIGNALAcquire Downstream Channel   843000000 Hz   Locked
Connectivity State   OK   Operational
Boot State   OK   Operational
Configuration File   OK   150001_vm2.0_d.cfg
Security   Enabled   BPI+
Downstream Bonded Channels
Channel   Lock Status   Modulation   Channel ID   Frequency   Power   SNR   Correctables   Uncorrectables
1   Locked   QAM256   2   843000000 Hz    0.2 dBmV   39.1 dB   1005   0
2   Locked   QAM256   3   849000000 Hz   -0.5 dBmV   38.7 dB   35   0
3   Locked   QAM256   4   855000000 Hz   -0.5 dBmV   37.4 dB   25   0
4   Locked   QAM256   9   867000000 Hz   -1.6 dBmV   37.9 dB   25   0
5   Locked   QAM256   10   873000000 Hz   -2.0 dBmV   37.9 dB   31   0
6   Locked   QAM256   11   879000000 Hz   -1.8 dBmV   38.0 dB   28   0
7   Locked   QAM256   12   885000000 Hz   -2.0 dBmV   37.3 dB   45   0
8   Not Locked   Unknown   0   0 Hz    0.0 dBmV    0.0 dB   0   0
Correctables   Uncorrectables
1139   0
Upstream Bonded Channels
Channel   Lock Status   US Channel Type   Channel ID   Symbol Rate   Frequency   Power
1   Locked   ATDMA   1   5120 Ksym/sec   25600000 Hz   43.2 dBmV
2   Not Locked   Unknown   1   0 Ksym/sec   0 Hz    0.0 dBmV
3   Not Locked   Unknown   1   0 Ksym/sec   0 Hz    0.0 dBmV
4   Not Locked   Unknown   1   0 Ksym/sec   0 Hz    0.0 dBmV
PERFORMANCEhttp://www.speedtest.net/result/1595729861.pngBoston 32.98 7.11 15ms
http://www.speedtest.net/result/1595732324.pngNew York 32.67 6.63 12ms
Philidaphia 22ms 1 ms A
Test Type:   Application Speed
Location:   
Download Speed:   32701 kbps
Upload Speed:   7259 kbps
Speed Consistency:   99 %
Round Trip Time:   16 ms
Max Delay:   2 ms
Average Delay:   1 ms
Bandwidth:   32800 kbps
Max Route Speed:   32767 kbps
Forced Idle:   6 %
Route Concurrency:   1
Test Type:   s / s
Round Trip Time Consistency:   88 %