I can't speak much to the practical aspects of trying to do DeployAnywhere imaging of these particular two machine models because that's really driven by the plethora of design faults and driver issues associated with the Optiplex line; no doubt others can speak more to that.
However, there's a user migration system built into Ghost Solution Suite built around creating a package of settings and files from the original machine and transferring it to the new one. What you see in the GSS console under "Configurations/User Migration Templates" is based on something created around Ghost 8.0 using AutoInstall, but from GSS 2.0 onwards this was powered by a different product sold separately for a short time as Symantec User Migration.
[ I don't recall off the top of my head whether all of the components from the standalone SUM are available in the GSS 2.5 installer or not, as what's visible in the GSS console GUI is a subset of what SUM can do. In GSS 2.0 there was a separate installer launched from the CD splash page to get the standalone SUM product bits on top of the subset visible through the console but I don't recall whether that was left in for GSS 2.5 or not. ]
With SUM it could be run through the console (using the slightly less flexible package template mechanism exposed there), or the standalone SUM package builder could be run to build a package which could be deployed through the console onto the new machines. Either way, using SUM you won't have to deal with all the various unique problems of the existing Optiplexes since the SUM capture process just runs in the existing operating system.
One small quirk of the console integration in SUM is that user package capture tasks build the entire captured package on the client machine, and then move it to the GSS server, so the machines do need enough free disk space to hold the package during that process. Otherwise there shouldn't be too much to choose between console-managed and standalone SUM migration.
[ Bonus history: Symante User Migration was built out of a product originally called "The Van", the maker of which had failed. During the planning for GSS 2.0, it was identified as important to completely replace the AutoInstall-based user migration system in order to enable good XP->Vista migration, and so the source code for The Van was basically a source-code-only acquisition from the liquidators. The Ghost team then did a lot of work to expand that base into what was then dubbed SUM and then merged into the Solution Suite console replacing the older system. ]
While in the short term it's attractive to just image, depending on what your organization's status is with respect to migration away from Windows XP it may well be a good idea explore this process instead so that if you do need to do any XP->Win7 work in future the basics are all in place.