Web Managed Procurve Sufficient For Important Edge Switch

I've been tasked with buying a "good" edge switch for my company's datacenter presence. After a full day of searching around and reading, I think I have decided on a procurve. The question now is what is sufficient for our needs.

We currently have 8 machines and will possibly add another 3 or 4 before the end of the year. We're running gigabit everywhere at the moment, and at bare minimum would need gigabit to 3 of our servers currently. Hopefully we will need gigabit to 4 or 5 servers by the end of the year.

Our website is of very high value to us, but we're also very much in the startup mentality of pinching pennies.

My question is if a web managed switch like the procurve 1800-24g has some performance/reliability downsides compared to like a 2810-24g managed switch. Looks like the 1800-24g can be had for about $400, and the 2810-24g for about $1300.

Searching around this forum, I saw a few references to the 1800-24g where the comment was that it would be great for a lower throughput need. Can anyone tell me why this would be insufficient for higher demands?

Our peak sustained throughput on the uplink to the hosting provider's router so far has been about 120mbps, and we hope to double this by end of year (and grow beyond).

If possible, I would like to be forward looking to the point where we will want to spend more money and have redundant switches in place to protect uptime. I do see that the 2810-24g is listed as stackable, but reading /rnd/pdfs/ProCurve_Stacking_Technology.pdf on HP's website (newbie not allowed to link in posts) seems to me to say that I wouldn't have any options for automatic failover to a slave switch with it. Does anyone know if this is correct?

Having a failover hot switch ready is not a deal breaker since we're only looking at switches that will give us high confidence in the first place.

How about comments on the wisdom of buying something like this used? My gut instinct is that I should avoid used since this is a high performance single point of failure for our entire internet presence. But I don't know how rock solid I should expect a used procurve to be.

In case you are wondering, our technical needs from the switch our modest. I will probably set up a vlan for each of our load balancing clusters to contain multicasting, but the only other feature I know of so far that I desire is the snmp reporting data.

I guess the root question is - would a web managed procurve leave me at a disadvantage for row performance or reliability compared to a full managed procurve?