Best to use a local agent to organise the basics - permit, deposits, sirdar, flights etc. You could get them to pre-arrange the porters, or if you're starting from Lukla you could do it on the spot. It would partly depend when you go and how much time you have. I haven't been to the Khumbu, but on my last Nepal trip I found having the agent pre-arrange porters was not more expensive, and significantly less hassle, than doing it myself - which I have done a few times, in Nepal and elsewhere.
I'm guessing if you went to Lobuche in April there is a good chance there would be other teams on the hill, easing any routefinding problems (!). This year Everest teams used it as acclimatisation and camped up on it. Note that most people don't go to the main summit, stopping before a notch. I would find this annoying. Obviously Mera Peak would be an easy choice, and have teams on it, but others like Kyajo Ri (from the south) and Parchamo might worth a look and should be familiar to agents, making them easier to organise. Cholatse is now an official Trekking Peak too. My last trip to Nepal, for an unclimbed 6000er, the agent and Ministry officials had to go look up where it was. Because ...
There are a number of 'Expedition Peaks' that, if they are under 6500m, thus requiring no Liaison Officer, and depending what season you go, are actually cheaper and less hassle than the official 'Trekking Peaks' (which require you hire a Sirdar/guide) - but not many people realise this. Some of these peaks are even unclimbed (not in the Khumbu, in other areas), but they are slowly getting picked off in recent years by people aware of the situation. I had a laugh with my agent (Tendy at IceLand Trekking) that it was cheaper for us to attempt an unclimbed 6400m peak and walk out through Mustang than it was to go just trekking in Mustang for two weeks. It's a bit silly, but such is the Nepal bureaucracy.
In that vein, one of the hassles of doing these trips yourself is things like trying to get your garbage deposit back. Commercial trips just factor the cost into the price they charge you and most never notice it. In theory it doesn't cost you anything, the $500 is just a deposit, but it might cost you a day or more of hassling in KTM to get it back. The agent probably won't do it for you as their margins on these kind of DIY trips are too slim to do more than the minimum. They'll just charge you the costs - permit etc - and a service fee - maybe $100 each or so - for their legwork and that's it. The rest is up to you. They make their money off fully catered, guided trips, full packages.