IMHO that depends on your experience and how far you want to push the envelope.
If you want to make great espressos I would go for something a little better with a boiler, perhaps a Silvia. You would have a bit of time between extracting and steaming as the boiler heats / cools (compared to a higher end machine, but probably not much worse compared to a thermoblock).
In my opinion the lower-end thermoblocks are easy to get wrong. It depends on your perspective (what youre used to drinking) and what youre willing to put into it - fresh roasted beans? Having said that I had a BES 820 for 2 years and was satisfied for quite some time... until upgraditis!
hope that helps!