Hmm... this is strange. You should be able to get an E3000 to sync with a UMSA. There must be something that's missing... I've tested many E3000 TVs before with this setup.
As Apple Annie said, Loewes produce a high quality image but they're not the most compatible chassis when it comes to the wide ranges of modelines that arcade games use. The bulk of 224p games with be fine but you'll be missing lines when you go up to 240 or 256 unless you manage to force the TV into PAL mode in which case games will run slower or play full speed using triple buffer (no smooth scrolling). There is information on my blog regarding the E3000 and also plenty on the GroovyMAME forum.
The upshot is that the image produced by an E3000 is extremely hard to beat. If you're mostly about 224p games (Neo Geo, CPS1/2/3, System 16 and many, many others) then you'll be very happy indeed.
Now, although I don't have an E3000 here I can test with, there are some setting you should look at. In the channel programming section of the menu system, there are options to setup the AV channel as PAL, NTSC, Auto, PAL-60, etc. You should definitely experiment there. From memory, the Auto option is probably best. Also, the TV works much better in Decoder mode rather than RGB. From memory, the RGB input option doesn't cope with interlaced modes well but the Decoder option does. It's been a while but I know those options are in there somewhere. Make sure you've got your SCART cable in the correct input also. Usually only one port is RGB capable.
The E3000 chassis has two sets of Service Menu settings: one for NTSC and one for PAL. You can set the geometry differently for each mode with is quite cool.
As der Apfel junge said, Grundigs are easier to set up since they cope with pretty much every refresh rate you send them. However, don't give up on the Loewe yet because it will look magic when you finally get it to sync.

Explore the channel programming section and try to get the CRT_emudriver to work. It can be done!